SMG Gearboxes

[Steve Gill]

Ok folks I've created this topic as a discussion point for the problems I've been having with SMG gearboxes. A brief summary of my problem:

I bought the car in August 2006, and everything was fine for the first while. Quite a few laps of the ring since then, but I'm not sure exactly when it first started happening, I think it was early 2008 because I first noticed it at the ring - crunching from 3rd to 4th. A good example on video was at Spa in May 2008: (http://www.vimeo.com/1093053).

The only relevant work to the car was the clutch (and flywheel?) were replaced in April 2007 by a German dealer, as the car was slipping and eventually died just outside the ring entrance, refusing to go into gears :(

I replaced the gearbox in June 2008, where we also put a race flywheel and clutch in as well :thumbs: It was all better for about a month or so, and then it started happening again :bigcry:

After much discussion with my local dealer, I eventually replaced the actuator in April and reinitialised all the software (including reflashing the SMG ECU), which on the road seemed better but as soon as I took it to knockhill it started again. So, annoyed by now, I replaced the whole gearbox AND hydraulic unit, thereby a process of elimination I'd replaced everything SMG gearbox wise with brand new parts. Only the pipes between the hydraulic unit, and the SMG ECU itself were the existing items. For information, I also think the gearbox temperature sensor wasn't replaced, but I'm going to try and find that out.

Anyway as most will know from my most recent videos, the problem started happening again (at my only trip to the ring this year, is that a coincidence?) and since then has got much worse. I've not driven as much on track this year, but I have done a few races. However I am not convinced the stress on the gearbox/SMG is any worse than the last few years, if anything its had a lighter workload.

I'm now in the process of working out what could be causing my problems. I think the gearbox needs fixed now, the syncro will be screwed, but I want to fix the source of the problem before repairing the box.

I've found a great resource online: http://www.leo.nutz.de/docs/bmw/smg_training_manual.pdf

From that I've worked out the following. I'd appreciate any comments or thoughts to help me!

----

The standard basic gearbox (S6S420G), as used in the M3, is transformed into a sequential gearbox with the addition of:
- a hydraulic unit (item 1 below - part number 21532229715)
http://img.photobucket.com/albums/v226/sgill22/CSL/250.png

- shift assembly/actuator (item 1 on the diagram below - 23412229789) http://img.photobucket.com/albums/v226/sgill22/CSL/241.png

- a special clutch slave cylinder (item 8 on the diagram below - 1522229841) http://img.photobucket.com/albums/v226/sgill22/CSL/250.png

- a new shift-lever module (item 1 on the diagram below - 25122283852) http://img.photobucket.com/albums/v226/sgill22/CSL/117.png

The SMG II Control Unit, installed in the E-Box next to the DME, is a single board module with SKE (134 pin) gray colored connectors (2360783772) http://img.photobucket.com/albums/v226/sgill22/CSL/125.png

Communication with the DME is via a dedicated CAN bus (SMG II CAN Bus) - could part of the problem be this communication wire(s)?

Based on instructions received from the DME the SMG II control unit manages the clutch solenoid valve (proportional directional valve), the selector shaft up and down solenoids (pressure control valves), and the selection angle solenoid (proportional directional valve). 4 solenoids in total, all on the hydraulic unit and therefore all brand new.

While the SMG II control unit receives many of the inputs and manages the control of the hydraulic system, the DME is responsible for and controls all gearshifts. Sensor inputs received by the SMG II control unit are relayed to the DME for processing and monitoring. I think this rules out the DME as it's evident with my problem that its trying to change gear, it's just failing whilst doing so.

http://img.photobucket.com/albums/v226/sgill22/CSL/SMG1.jpg

Problem elimination / narrowing down:
- Score out the keylock, nothing to do with that.
- The Canbus between the SMG and DME - could that be faulty?

Signals exchanged via SMG CAN Bus:
Engine Speed: The engine speed signal is transmitted twice to the SMG II control unit. One signal arrives via the SMG CAN, the other arrives via a hard wire from the DME.
Engine Coolant Temp, Engine Oil Temp and Intake Air Temp:The signals are inputs directly into the DME and are shared with the SMG II control unit as the information is needed over the SMG II CAN.
PWG: The PWG signal is input into the DME and forwarded to the SMG II control unit. The information is used to calculate engine load.
EDR Feedback Pots: These potentiometers provide throttle position information that is useful during slip intervention.
Wheel Speed: Conditioned digital wheel speed information is received from the DSC control unit. The SMG II control unit uses data from all 4 wheels to detect vehicle speed and wheel slip in the A-Mode and during down shifts in all modes to detect drag torque induced wheel slip. I think this can probably be scored out as it mainly relates to the A mode, but relates to down shifts in S modes as well. The original problem I had was during upshift from 3rd to 4th, so I'm presuming this can be scored out.
Transverse Acceleration: Transverse Acceleration data is transferred from the DSC control unit in the A-Mode so that up and down shifts may be prevented during high speed cornering. This sensor information is further evaluated for slip recognition purposes. I think this can be scored out as it relates to automatic gear changes i A mode, I use S (manual) mode all the time.
Steering Angle: This data from the steering angle sensor is sent via the CAN Bus for cornering and slip control information.
Cruise Status: The cruise mode is deactivated when a driver initiated shift is made in the S-Mode, during A-Mode operation, the cruise control setting is maintained. This is scored out as the CSL doesn't have cruise, and we're talking about S mode.
Parking Brake: Information concerning parking brake application affects gear engagement and vehicle operation. I suppose its possible that a faulty sensor is telling the system that the parking brake is engaged, stopping it engaging gear, but the chances of it only happening occassionally and only on 3rd to 4th I think are very unlikely so I'm scoring this out.
Door Contacts: The hall effect door position sensors integrated into the door latch mechanism signal the GM. This data is transferred via the K-Bus and CAN Bus for safety program initiation. Scoring this out as this is only for safety telling if the door is open or not. I have seen the gear display flash because the door is ajar, but it still changes gear OK regardless.
Brake Light Switch: Brake pedal status is transferred to the SMG II control unit via the DME. The signal is used for:
- Unlocking the shift lock
- Brake detection
- Engine Starting
- Downhill detection
- Clutch Disengagement while stopped.
Scoring this out as I'm not braking when changing from 3rd to 4th!!
- Score out the MFL shift up and down, don't think thats the problem (although I did have problems at Brands at Donnington where it wouldn't respond to the paddles and I had to use the gear lever - seperate problem or related?)
- 8 x shift lever hall sensors - what are these? Have they been replaced?
Located in the shift lever module, 8 hall sensors detect upshift and downshift requests and are also used for Selector Lever position indication (Forward, Reverse and Neutral). Signals from the hall sensors are also used to initiate mode changes from S-Mode to A-Mode and back.
- Score out drivelogic control
This is the switch located on the console just to the rear of the shift lever, scoring it out as its only a switch telling the computer which program to choose for the speed of gear change.
- Longitudinal acceleration sensor, not convinced its anything to do with this, but was one of my errors to do with this before?
The signals from the Longitudinal Acceleration Sensor which is mounted under the passenger seat are used for uphill driving programs.
Scoring this out as I think it's only relevant to the A mode, for uphill information.Very unlikely to be relevant unless the 3rd to 4th changes were only ever uphill, which they weren't!!
- General Module (I think this is the SMG module) - not been replaced, could this be the problem?
Load deactivation information (Sleep) is received by the SMG II Control Unit. Not sure what this means?
- Transmission input speed sensor - has this been replaced?
A hall sensor is used to measure transmission input shaft speed.
- Potentiometer Clutch - what is this? has it been replaced?
Input from the PLCD providing exact clutch position. The PLCD has been replaced so I'm scoring this out.
- 2 x Selection angle cylinder POTs - think these are part of the actuator and therefore replaced
The Position sensor provides two inputs (PS2 is the selection angle sensor, a dual pot) for position recognition of the main selector shaft in the transmission.
- 2 x Shift travel cylinder - think these are part of the actuator and therefore replaced
The Position sensor provides two inputs (PS3 is the shift travel sensor, a dual pot) for position recognition of the main selector shaft in the transmission.
- Transmission temperature - replaced?
An NTC sensor is used to measure Gearbox oil temperature.
- Hydraulic temperature - replaced? (number 7 on the diagram below)
An NTC sensor is used to measure hydraulic fluid temperature.
- Hydraulic pressure - replaced? (number 8 on the diagram below)
A Pressure transducer for monitoring hydraulic pressure sends pressure information to the SMG II Control Unit.
- Hood microswitches - score them out not the problem although they have caused problems in the past, slamming the bonnet down solves it :)
Two Micro switches located in the hood latch mechanism provide a ground signal to the SMG II Control Unit when the hood is closed. Richard from Thorney's had mentioned about getting a better ground signal, related?
- TD Signal Engine RPM comes from the DME, I presume this is not the problem.
Calculated engine speed received from DME via hardwire serves as redundant information with that received via the SMG CAN Bus. Could it be relevant?
- Score out the shift lock, its not the problem.
The Shift Lock Mechanism locks the shift lever in position for parking and prevents
unintended gear changes as part of the safety programming.
- What is the EWS module, could this be part of the problem?
During the start-up operation, the SMG II Control Unit confirms shift lever position (0) and brake application and signals the EWS module which then allows starter engagement. Scoring it out as the problem is not about starting the car!
- Hydraulic pump, which has been replaced. Could it be the salmon coloured relay that keeps the pressure in the hydraulic pump between 45 and 80bar? Has this relay been changed? I should carry spares of this relay.
The Hydraulic Unit is energized through a relay controlled by the SMG II Control Unit. The operation of four (4) solenoid valves located in the hydraulic unit that are used to actuate the clutch and shift the transmission are also controlled by the SMG II.
Detailed diagram of the hydraulic unit:

http://img.photobucket.com/albums/v226/sgill22/CSL/smg2.jpg

1. Hydraulic Line for Shift Travel 1 Gears 1,3,5.
2. Hydraulic Line Slave Cylinder Clutch Control.
3. Hydraulic Line for Selector Angle Control Cylinder.
4. Hydraulic Line for Shift Travel 2 Gears 2,4,6.
5. Pressure Accumulator.
6. Supply Line from Hydraulic Tank.
7. Hydraulic Fluid Temp Sensor
8. Hydraulic Fluid Pressure Sensor.
9. X 5330 18 Pin connector.


Just noticed on the detailed diagram that there is a seperate hydraulic line for gears 2, 4 and 6. Tom from Thorneys said he couldn't get the autologic machine to go into those gears. Coincidence? According to the diagram below

http://img.photobucket.com/albums/v226/sgill22/CSL/smg3.jpg

one line moves it into 1st, 3rd or 5th, and the other releases pressure(?) to move it the opposite way into 2nd, 4th or 6th.

Were the pipes from the hydraulic unit to the gearbox replaced? I need to check but I don't think so. Could they need cleared out?

page 27: "The forces required for shifting are strongly dependent on gearbox-fluid temperature. The fluid pressures acting on the pistons of the two shift cylinders are adapted according to fluid temperature."
I dont think the gearbox temperature sensor was changed? Perhaps the gearbox oil is getting too hot? Why are other CSLs not having this problem though?

[DuncanR]

Steve, me being an expert on CSL's having owned one since Friday just gone ! Im probably of little use !, however,I do mess about with hydraulics from time to time, reading through your problems you dont say if you replaced the oil cooler (have assumed they have one) or if you flushed the matrix out, it could be that its bunged up with sludge, and not working as efficiently, giving a rise to increase temperature. The double wammy could be if the temp sensor is also U/S. Just trying to assist with a bit of logic if i can !

[Steve Gill]

Steve, me being an expert on CSL's having owned one since Friday just gone ! Im probably of little use !, however,I do mess about with hydraulics from time to time, reading through your problems you dont say if you replaced the oil cooler (have assumed they have one) or if you flushed the matrix out, it could be that its bunged up with sludge, and not working as efficiently, giving a rise to increase temperature. The double wammy could be if the temp sensor is also U/S. Just trying to assist with a bit of logic if i can !
Exactly what I'm looking for Duncan, so thanks for the reply. I'm too close to the situation, can't see the wood from the trees, and my techy knowledge is worse than my driving (not saying much :hahaha:).

There is no oil cooler that I'm aware of - either for the SMG oil or the gearbox oil. Certainly not as standard.

Not sure what matrix you're talking about?

I'll look into the sensor, it might not be helping, perhaps reporting temperature as OK when its actually warmer and requires more SMG pressure to the actuator?

[shimmy]

Steve

i have a video of my CSL gearbox doing exactly the same thing in 2007 at Donington. Caught it on film 3 times in one trackday missing 4th gear from 3rd only

BMW Murketts saw the film, checked the gearbox and said it was just starting to wear out the synchro and gave me a new SMG gearbox on goodwill

no problems ever since.

[DuncanR]

If it had a cooler, the matrix is the sort of element inside similar to a rad, and sometimes they need flushing out. Im surprised that this gearbox doesnt have one given the stick it takes !, if it had one, it would at least help to keep the oil temp in some sort of limited band of temperatrures, good luck mate !

[AlexGTT]

Steve, a faulty gearbox oil temp sender sounds possible, as does the pump relay you mention. Is there any way a diagnostic reader could isolate faults with those individual components? Would be interesting to see what codes have been thrown up when the diagnostics are checked. It's worth a swop of those components, individually to accurately diagnose. Probably the cheapest items to change on the whole SMG system!

[NZ_M3]

Pump relay's related to the start up procedure and keeping the hydraulic unit at operating PSI (i.e. the noise you hear when you first open the door if it's not). Just open your fuse box and check that you have the updated 'salmon' colour relay.

What clutch are you running? I know a lot of the US guys have problems running aftermarket clutch paks in SMG cars and even more so when they go force induction. This could be your problem (as the SMG control unit is programmed for a certain set parameter for the OEM clutch pak, so if your pressure plate has double the clamping load it could mean that it's not disengaging the clutch properly before it shifts gear, so over time you'd get premature synchro wear and eventually the gear selection issues)

Check that all the hydraulic hardlines are kink free - a tech may have inadvertently bent a hydraulic line when doing a pump install or even from pulling the gearbox out (I've seen it happen before).

Definitely also sounds to me like the gearbox is getting too hot - these SMG gearboxes really need a cooler unit of some sort in my opinion.

Another possibility - broken compression spring (part #6) - see post number #32 http://www.m3forum.net/m3forum/showthread.php?p=3497344#post3497344

http://www.realoem.com/bmw/diagrams/w/u/188.png

Also check that item 10 below has been changed - this is unique to the SMG gearbox.

http://img.photobucket.com/albums/v226/sgill22/CSL/241.png


One more thing .. no doubt you've read this post on m3forums already? Quite useful for trouble shooting

http://www.m3forum.net/m3forum/showthread.php?t=231113

[The Gorilla]

Hi,

I have read many views and opinions on the SMG Gearbox
and reasons as to what causes the issues.

Lighter flywheels do not work well with SMG as the inertia
is altered and it can cause puluse issues with the software.

No such issues on a manual car, same gearbox internally.

My own view is that the SAC Clutch and being of poor design
is at the start of the SMG woes.

The SAC was designed so that clutch take up should be about
the same as the clutch wears.
This should be ideal for an SMG car as it should produce the same
clutch shift pattern time and time again.
Something that actuators and the hydraulics function best with.

However, once the SAC incurrs wear, its clutch travel can alter
then you have accuators and even more importantly hydraulics
which can be a fraction out of sequence which can bring on
issues such as clutch 'slur' and delays before engaging either up
or down in the shift pattern.

The Software can only react to the input signals it receives, rpm, etc.

So once you have hydraulics that are a fraction out of sequence
then you will incur increased wear in the gearbox syncro rings, and
this will then lead to pump fatigue, as the selection process
is being forced as opposed engaged.

On a normal road car, its progressive over a period depending on use etc,
but on a Track / Race car, given the extra shock and load that is pushed
through the drivetrain, the attrition rate and wear is much faster.

I do not believe that there is a way to ensure that the Clutch Travel
is perfected time and time again, on a SMG car,
and thus these problems on Cars that see hard use
will be a by product of that use.

Harder Clucth disc, like Cerametallic as opposed Organic helps to slow
down the wear rate, but the shift changes become more agressive
for a Car that is driven on the raod as well.

Just my thoughts.

Regards,

The Gorilla.

[The Gorilla]

Hi,

I should have added that gearboxes, SMG included
suffer most wear and at most
risk of damage etc when the clutch is in, not out.

Regards,

The Gorilla.

[shimmy]

Hi,

I should have added that gearboxes, SMG included
suffer most wear and at most
risk of damage etc when the clutch is in, not out.

Regards,



The Gorilla.

would getting the gearbox reprogrammed/retaught in a regular basis help

[_Nathan_]

Can you recommend a Cerametallic friction plate please?

I'm fitting a gearbox cooler to mine, the main issues I had were 5th to 4th downshifts crunching, not sure if that could be because I was changing down a bit early in the braking sequence and the SMG logic can't cope with the 4.1 final drive? Got an overrev to 8436rpm on one crunchy downshift.

[NZ_M3]

'The Gorilla' ... Steve never said what brand of clutch he's using - you are assuming that he uses a Sachs race clutch pack.

The factory OEM clutch kit is made by LuK, not Sachs - get your facts right :banghead:

The self adjusting mechanism on the pressure plate doesn't change the distance that the clutch slave actuator moves when the clutch disc is worn - the adjustment is done via a spring mechanism internally of the friction contact plate, the fingers on the pressure plate moves the same distance throughout the life of the clutch pack. What changes is the take up point which is what the automatic adjusting mechanism is doing. And it is also what the clutch reinitialisation does when the car's hooked up to the GT1 - it reinitialises the take up point not the disengagement point - that is constant.

What you are saying is incorrect - as the disengement of the clutch is the same - so when the hydraulic shifts gears the clutch will always be disengaged. It is the take up that causes issue with aftermarket clutch packs (go and read the American forums, it has a detailed analysis on why high clamping pressure plates causes issues).

[The Gorilla]

Hi,

Hi- NZ_M3 - I do not agree with what the ''Americans' have to say
on this issue, sorry.

If I remember correctly you also dismissed the rear turret reinforcement
rings from the Z3, saying they would make no difference ?

The SAC Clutch is a bad design, go ask any E39 M5 owner or Forum
on SAC standard clutch which is the same poorly designed component.

The wear in the clutch is adjusted via a nylon strip within the SAC
pressure plate, so as to try and compensate for the wear in the disc.
This was designed to make the engagement travel of pressure plate
to clutch the same as the disc wears.

Of course as these two components wear and the SAC tries
to keep the distance bewteen disc and flywheen the same the
travel distance of the hydraulics increases as the disc is worn.

Once a slight mis-alignment starts to ocurr due to wear etc, then
the acctuators still function on pulse signal, inputs etc,
and the pump is told shift, it has no way to compensate for any
slight mis-alignment or wear 'ie slack' in the system.

On a manual car the SAC clutch adjustment when worn is
to a degree compensated by the driver inputs, and the shift
pattern to an extent can be altered to suit.

Shimmy- I do not think that re-programming the Gear box ECU/Software
would make much difference once the clutch has worn past a certain
point, go to the Hewland website explains a lot about gearboxes.

Nathan- The Sachs uprated Pressure Plate and the uprated Clutch
Disc used with Standard Dual Mass Flywheel have brought about
quite good results.
Some who use their cars for Track and Road run the Sachs Pressure plate
and the standard S54 Clutch Disc as a compromise.

NZ_M3- I do not think I assumed anything on Steve Gills clutch.

Regards,

The Gorilla.

[_Nathan_]

thanks.

My car isn't used on the road any more so happy to go with the uprated disk and pressure plate if you've used it with SMG without issue.

Don't suppose you know the part numbers? Sorry to be a pain.

[The Gorilla]

Hi,

Nathan- Sach Uprated Cover is 083082 999791
fits the std Dual Mass 240mm S54 Flywheel.

Make sure it is S54 as the S50/ B30/32 are also 240mm
but have a Pressure Cover bolt pattern that is not quite the same,
and do not fit the S54 Flywheel.

You will have to check with Sachs as I think they have
changed the Part numbers on the Discs ?

Their Organic Disc which is good for 570nm / 422 lb/ft
was part number- 891964 999978 and is a little better than
the std OEM BMW Clutch Disc.

As a note of interest a lot of the Diesel BMW's at 525cc and larger
run the same clutch disc as the M3 but with just a different centre
mount.

As the Diesels make far more Torque lower down the rev band,
its interesting the loads the standard OEM disc can take.

I run a Gearbox oil cooler, but much for the wear on the
Transmission components at higher temps,
than making the clutch operate better.

Regards,

The Gorilla.

[_Nathan_]

Thank you.

Did you weld seperate take offs for the pipes in to the box or adapt the filler hole and sump plug to accept return and pump feed respectively, trying to weigh up the best way of doing it versus trying to do it cheaply ;)

[NZ_M3]

Hi,

Hi- NZ_M3 - I do not agree with what the ''Americans' have to say
on this issue, sorry.

Fair enough - I don't agree with everything they have to say about the M3s - but majority of them know more about the SMG system than you do I must say. But I'll entertain.


If I remember correctly you also dismissed the rear turret reinforcement
rings from the Z3, saying they would make no difference ?

And I still say they make no difference - a stress induced failure will take time - time will prove me right that if you run a full coilover setup on the rear of the E46 coupe chassis without a full cage or the likes to spread the load then it's only a matter of time before the rear shock tower tears itself apart.



The SAC Clutch is a bad design, go ask any E39 M5 owner or Forum
on SAC standard clutch which is the same poorly designed component.

I agree - I never said the Self Adjusting Clutch was a good design (made worse by the Clutch Delay valve that BMW insists on putting in their cars) - I am simply saying your technical explanation is incorrect ... the forums are for sharing information, and I am simply pointing out inaccuracies that you are putting across. For example your explanation below of how the Self Adjusting mechanism works - it couldn't be further from the truth


The wear in the clutch is adjusted via a nylon strip within the SAC
pressure plate, so as to try and compensate for the wear in the disc.
This was designed to make the engagement travel of pressure plate
to clutch the same as the disc wears.

The self adjusting mechanism works off a spring and ramp ring design - i.e. it rotates in or out to compensate for the wear:

Here it is directly from the manufacturer - as I said, the OEM clutch pack is made by LuK


Since clutches are subject to wear during use in the vehicle, LuK, as the first clutch manufacturer, put a great deal of effort into developing a type of wear compensation system for the clutch, and put it in production in 1995. The self-adjusting clutch SAC uses a load sensor (sensor-diaphragm spring) to activate its wear compensation by turning a ramp ring. This compensation mechanism has made it possible to decrease operating loads. The compensation for the clutch wear has also made it possible to increase the clutch service life by about 1.5 times without any significant change in the operating load over the service life. The wear adjustment system of the SAC – consisting of the sensor-diaphragm spring (load sensor) and the deep-drawn steel adjuster ring – is characterized by very high functional precision. Since a harmonic operating load curve is required in addition to comfortable clutch operation, the SAC was created with the capacity to be tuned to specific vehicle characteristic curves. One of the mechanisms that makes this possible is the compensation spring, which can generate the flatter characteristic curves that are frequently desired.
The newly developed SAC II.

provides a further optimization of the system. Here, the load sensor is not comprised of a second diaphragm spring, but rather of the sensor fingers formed from the main diaphragm spring and special tangential leaf springs with a decreasing characteristic curve.




Of course as these two components wear and the SAC tries
to keep the distance bewteen disc and flywheen the same the
travel distance of the hydraulics increases as the disc is worn.

Once a slight mis-alignment starts to ocurr due to wear etc, then
the acctuators still function on pulse signal, inputs etc,
and the pump is told shift, it has no way to compensate for any
slight mis-alignment or wear 'ie slack' in the system.

On a manual car the SAC clutch adjustment when worn is
to a degree compensated by the driver inputs, and the shift
pattern to an extent can be altered to suit.

Wrong again .... If what you are saying is true, then as the clutch disc wears the distance required to 'disengage' (or open) the clutch should be shorter (i.e. it takes less pedal travel to disengage the clutch as there's less material between the pressure plate ring and the flywheel due to the clutch plate wearing down). The opposite would be true when closing the clutch or engaging the clutch as there's a larger space for take up - that is why when clutch wears out the clutch pedal take up point (or bite point) is higher in a traditional 3 pedal manual car.

I can assure you that the hydraulic clutch slave actuator pushes the clutch in (to disengage) the same distance everytime through out the whole life of the clutch - the software initialisation only adjusts the take up point (i.e. to engage the clutch) ...

Here directly from the SMG training manual:

The Clutch Slave Cylinder is an innovative and new feature of the SMG II. The component consists of a slave cylinder with an integrated sensor housing. The sensor termed PLCD (Permanent Linear Countactless Displacement) measure clutch release travel



Shimmy- I do not think that re-programming the Gear box ECU/Software
would make much difference once the clutch has worn past a certain
point, go to the Hewland website explains a lot about gearboxes.

Again wrong as above.


I am aware that Sachs has brought out a new clutch pack that works on both manual and SMG vehicles - I've yet to try it or read the specs on it - but my suspicion is that it has an uprated friction plate rather than an increased pressure plate clamping force. But I'll need to read the specs to be sure.

[The Gorilla]

Hi,

Nathan- on the Gearbox oil cooler in and out feeds
I used the bottom drain plug for the feed out,
and the side plug for the return.

Banjo fitting for feed out, with the lug cut down to
keep the fitting as close to the box as possible,
and a new blanking bush for the side, with a Goodridge alloy T
so that I could run my Gearbox temp sensor as well.

NZ_M3- Your entitled to your views and opinions, but please
read and understand what I have said.

By the way I beleive the manufactures of the Titanic said it
was, quote, '' Unsinkable''.

Regards,

The Gorilla.

[shimmy]

dear Gorilla and NZ_M3

i do find both of your threads and posts very interesting and full of technical info that most of us here, and tbh most of the BMW specialists we know would not understand

however you both seem to constantly disagree with each others techinical opinions on nearly every subject even subjects that can only have one answer

now i am not a mechanic or even a person with car knowledge more than a few skils like changing brake pads and wheels and occassionally a disc or two, but i am qualified as a Project Manager and understand when i am being fed bullshit on a monumental scale.

So for my peace of mind and so i get some sleep without worrying if my rear turret is gonna split or if my chassis is gonna twist or if my gearbox and clutch is gonna piss itself all over the floor can which ever one of you that is guessing (note my careful choice of words) please stop and let the other tell us the truth!;)

[_Nathan_]

Thanks very much - that was the answer I was hoping for (as it doesn't involve too much labour!).

[glendog74]

dear Gorilla and NZ_M3

i do find both of your threads and posts very interesting

I'm off to bed... :whistle:

[AlexGTT]

dear Gorilla and NZ_M3

i do find both of your threads and posts very interesting and full of technical info that most of us here, and tbh most of the BMW specialists we know would not understand

however you both seem to constantly disagree with each others techinical opinions on nearly every subject even subjects that can only have one answer

now i am not a mechanic or even a person with car knowledge more than a few skils like changing brake pads and wheels and occassionally a disc or two, but i am qualified as a Project Manager and understand when i am being fed bullshit on a monumental scale.

So for my peace of mind and so i get some sleep without worrying if my rear turret is gonna split or if my chassis is gonna twist or if my gearbox and clutch is gonna piss itself all over the floor can which ever one of you that is guessing (note my careful choice of words) please stop and let the other tell us the truth!;)

Very succinct, yet still diplomatically expressed Shimmy. ;)

I'm off to bed as well! :smt039

[The Gorilla]

Hi,

Shimmy- my views are always expressed from first hand
experince and things that have happened to my cars.

Just for the record, a Lightweiight flywheel [12lbs] with
a Sachs Uprated Clutch Disc and cover was fitted to my Car, CSL.

It was dreadful, so the Gearbox ECU was reprogramed with the
latest version of the software, no change.

Then the SMG pump fluid was drained the system was flushed and
refilled. No change still would not engage properly, the upshifts and
downshifts were all hit or miss etc.

So the Lighter flywheel was removed, the dual mass refitted, with
the Sachs clutch, and the car has its moments but by and large its
OK. Can still get a small 'slur' now and then without sport or DSC off.
Now done around 1500 hard miles, its only used for Track days and the
odd local blast when trying things out, and its been OK.

I also have a E30 M3 with a CSL S54 engine Motec M800 and Drenth sequential Gearbox running a Dual disc 184MM Clutch with a 10lb
alloy flywheel, and a central clutch cylinder, which on the 'flatshit'
makes the SMG feel very slow.
This car does not run the 'E,Gas' or Fly by wire, but is running a throttle
cable/Linkage, which out of slower bends does allow a quicker pick up.
The S54 without the dual mass flywheel is far more responsive at lower revs
that its a shame that the SMG will not function correctly
with a lighter flywheel.

I did look into lighter dual mass flywheel in steel, but the savings
were not more than around 2-3 Kg which was not worth the costs.

Pectel have now developed a plug and play standalone for the S54 which
has been mapped specifically for the E.Gas, fly by wire, and in therory
will always have the throttle and air optimised as its rev matched and
picking up signals from engine load etc.
Interestingly they do not recommend SMG on a Car running this system.

Regards,

The Gorilla.

[NZ_M3]

I also have a E30 M3 with a CSL S54 engine Motec M800 and Drenth sequential Gearbox running a Dual disc 184MM Clutch with a 10lb
alloy flywheel, and a central clutch cylinder, which on the 'flatshit'
makes the SMG feel very slow.


why Hell ... you win Gorilla ... I can't compete with somebody with a car like that :thumbs::thumbs: That's awesomeness right there ... even more awesome if you did the work yourself :supz:

Would love to see some pictures of that beast !!!

How much did the drenth sequential cost? I've always wondered if it'd take much to convert the SMG in the CSL to the Drenth sequential (for track use of course, one'd be almost crazy to drive that gearbox on the road).

Oh and just for the record so that I am not seen as talking out of my ass ... I am not a mechanic by trade, but am self taught. Mostly to do with Hondas, but the basics are all much the sameness. I've personally done and completed 2 x auto to manual conversions, 2 engine rebuilds, numerous wiring and mechanical jobs on hybrid motor swaps for Hondas (much harder than it sounds) and am competent at changing a clutch on my own in a Honda (I've done it in record time of just under 3 and a half hours by myself on a B series with the engine in the car - dealerships quote 7 hours for the job) - but that's just monkey work I suppose.

I gather most of my knowledge on the M3 from personal experience and from reading training manuals when available - most other sources and knowledge I've built up over the years from reading forums and having 3 close friends who are master BMW mechanics - so what I don't know I just ask.

[_Nathan_]

Drenth is about £10k+VAT, but I can't see how you could get ignition cut for flat shift without a new ECU and therefore loom.

Believe you also need to mess about with starter motor too as the Drenth bell housing moves it I think.

Would love a Drenth + paddle shift mechanism. One day...

[NZ_M3]

Drenth is about £10k+VAT, but I can't see how you could get ignition cut for flat shift without a new ECU and therefore loom.

Believe you also need to mess about with starter motor too as the Drenth bell housing moves it I think.

Would love a Drenth + paddle shift mechanism. One day...

Cheers for that.

Yeah I figured to put in a Drenth you'd have to go aftermarket ECU and disable the traction control or run a different software perhaps?

We can always dream !! If only money was no object :hahaha:

[_Nathan_]

Motec will do traction with variable slip so that could be covered if you wanted. You'd also have to consider motorsport ABS units.

Basically a complete rewire of the car with a new loom, not the work of an afternoon!

Approx 50 hour inspection interval too, expensive business.

Occasionally you see second hand DG400s come up in europe but the actual box price isn't quite so significant when you add every thing needed up together.

[The Gorilla]

Hi,

NZ_M3 - There are no winners, we are all just Petrol Heads
spending our hard earned cash on metal boxes that have
components in them that every now and then seem to fail.

If I ever get to NZ to see a colleague on South Island, Conrad,
who races a E30 M3 with 2.5 S14 then the beers are on me.

It was about a 2 year build project on and off, did all myself
except the Paint Sparying and the MOTEC M880 loom, ECU Etc.

Its a S54 CSL running Motec M880 ECU, Plasma Coils, Bosch Ignition
Drivers, Vanos deleted, Dry Sumped with Oil/water heat exchangers.
twin 60mm exhaust with side exit and no Cats.
Drenth 6 speed DG400 Sequential, with DTM Alloy Cased Rear 3.73 LSD,
ZM3 Coupe rear arms with Bilstein Alloy Remote adjust Coil Overs,
fronts are 92 DTM Titanium Uprights, with Remote adjust 2 way coil
overs, Intrax Camber plates, Grp A Adjustable Front Arms, front and
rear ARB's are Cockpit adjustable blades, Manual 2.3 lock to lock rack,
and its runs on 92 DTM 9X18 Centre locks etc.

Shell is full weld in Chromoloy Cage with Carbon wings, bonnet, boot,
Polycarbonite windows, heated front screen,carbon door cards, full
flat floor underneath in Carbon, and it weighs wet without driver 1075kgs.

Its making about 370 BHP, rev limited to 8350, as its turned down a bit
just for engine longtivety, hopefully.

The hardest problem was cutting all the bulkhead and getting
it right so that the S54 engine sits about 70mm further back
than when others have done similar 6 cylinder conversions into
the E30 M3.

I learnt a lot when I did a road E30 M3 with a S50B32/ 6 speed box, which
I have just sold to a Guy in Hong Kong, it was a RHD build.

I will post some pics up shortly, if I can get them to load.

Regards,

The Gorilla.

[AlexGTT]

Would be very interested to see pictures of those motors Gorilla.:thumbs:

[Bealo]

Now that sounds like a hell of a car and a lot of fun on track.... :thumbs:

[Thorney]

Getting back to your question, do you run a gearbox cooler? I cant remember with all the other stuff we've looked at as we do on my car and we've not any any such problems on a stcok flywheel, gb and clutch thats been in the car for the last race season and previous 35k road miles.

[Steve Gill]

Getting back to your question, do you run a gearbox cooler? I cant remember with all the other stuff we've looked at as we do on my car and we've not any any such problems on a stcok flywheel, gb and clutch thats been in the car for the last race season and previous 35k road miles.
Didn't know you ran a gearbox cooler John! The more I've looked into this, the more I think its gearbox oil temperature related. Do you run the OEM gearbox oil, or do you run something else?

Can you supply details of what you've done to install the gearbox oil cooler?

[The Gorilla]

Hi,

I have Gearbox Oil and Diff oil temp in my car
as well pumps/coolers.

You would be surprised the temps in the gearbox
on a warm 32c plus day can reach when your pushing
the Car on a Track.

I have said before, this is due to the 'Thermal store'
created by the Alloy of the gearbox housing.

Once the gearbox oil has reached temp, its the
thermal store that will continue to raise its temp.

By re-circulating the oil away and back again you
not only reduce oil temp, but you ensure that the
Thermal Store does not continue to absorb heat,
as its primary heat source is now being cooled.

Regards,

The Gorilla.

[Hypnotic]

Had same problem with mine, it was as if the box tried to change gear without dippin the clutch ,BMW replaced the box and then clutch and flywheel ,with previous to that ,the rear axle/diff. All been fine since.
Good luck.

[mil]

Hello everyone,

Google guided me to this thread and as here seem to be many people with knowledge I decided to register. I hope it's ok to return this "old" thread.

Anyway my car has this very same problem and surprisingly the history sounds very similar to what Steve has been experiencing. The issue has not been solved but I want share my experiences if someone finally manages to find the root cause for this problem.

Everything started when the clutch was replaced. There was nothing "broken" with it as far as I know, but it was suspected to be quite used after 110000 km and plenty of track use and it was slipping a bit. I never had any problems what so ever with original components and that mileage. With new OEM clutch I had the first failures to shift to 4th gear pretty much immediately with this famous grinding noise. After that SMG adapation program was done again and it might have helped for some time. This problem never appears in the ECU logs, no error codes what so ever.

I did quite a lot of searching in the net and many people had reported that similar problems were fixed with new gearbox. So that was done. Ridiculously expensive work regardless of some compensation by BMW. So I was not too pleased when the problem came back on the second day after gearbox replacement. This happened in completely normal driving on street. This is why I suspect that this has nothing to do with gearbox itself and it should not be replaced. I got complete remanufactured gearbox, all new fluids, with all new SMG sensors. At least this is what they tell me. :)

After that SMG software was updated to the latest and SMG adaptation was redone. The software was the first thing that had a small impact. Car was running ok for maybe one month. At this point I was at Nurburgring and I ran into Schirmer Motorsport, which is BTW absolutely great place. According to Mr. Schirmer it should work with new clutch and gearbox. As my car had so high mileage, we decided to replace all suspension rubber bushings including rear differential mountings, with uniballs and Schirmer's aluminium bushings, as any clearance in the transmission could have an impact. Great modification BTW, but it had no help with SMG issue.

Now everyone seem to be pretty much out of ideas.

Hypnotic, you mention that you have replaced also rear axle/diff + everything else. Is it still working and what was the component that fixed it?

My car is standard E46 M3, but as these parts are more or less identical, I don't think it matters. Now I'm thinking going back to the clutch / flywheel section. Maybe it's all there where it started..

Any help or ideas are more than welcome.

//mil

[shimmy]

£5 spring

I'll find the tech details when I am back on the PC

[NZ_M3]

£5 spring

I'll find the tech details when I am back on the PC

I mentioned it on page 1

http://www.cslregister.com/forum/showpost.php?p=31931&postcount=7

[mil]

shimmy,

I'm aware that this small spring is important, however I'm under impression that it fixes cases where it is slow to change to 4th gear but there is no mechanical noise. Maybe that's different problem...

I did specifically ask that new gearbox also includes this spring and the answer was yes. So the spring should be ok. Would be worth of checking anyway when opened next time.

[shimmy]

This is why I suspect that this has nothing to do with gearbox itself and it should not be replaced. I got complete remanufactured gearbox, all new fluids, with all new SMG sensors. At least this is what they tell me.



i read this to mean that the gearbox was reconditioned and not NEW. If new it shouldnt be the spring i agree

have you seen this

http://www.m3forum.net/m3forum/showthread.php?t=231113

[Steve Gill]

i read this to mean that the gearbox was reconditioned and not NEW. If new it shouldnt be the spring i agree

have you seen this

http://www.m3forum.net/m3forum/showthread.php?t=231113
Shimmy all BMW supplied gearboxes are classed as reconditioned - I'm told that the whole internals are brand new but the case is reconditioned. When I bought a new gearbox from BMW that was all I could order - there wasn't a choice of new or reconditioned.

It did look shiny though if that helps :whistle: :hahaha:

[shimmy]

Shimmy all BMW supplied gearboxes are classed as reconditioned - I'm told that the whole internals are brand new but the case is reconditioned. When I bought a new gearbox from BMW that was all I could order - there wasn't a choice of new or reconditioned.

It did look shiny though if that helps :whistle: :hahaha:

i like shiney :beer:

[mil]

shimmy,

Yes I've read the troubleshooting thread. Good info, but no obvious solution to my issue there.

Spoke yesterday to one expert who was thinking that this could be caused by aftermarket software in my ECU (by Kelleners). He said that SMG and engine ECU will not communicate properly and SMG reset/adaptation is not possibly executed properly. Could be possible, but sounds bit strange, as it worked ok for years. However during that time I did not have to reset SMG ever.

Are you guys with the same issue running stock software or something else?

[TANKSLAPPER]

You may have a point here

I never had to reset my SMG in my current csl which has got a chipped ECU

but my previous CSL had an reset every time it went to the dealers.

[mil]

Small update: it's most likely not ECU software related. Found at least one case in US with all the latest OEM software and still failing occasionally - less frequently though.

[Steve Gill]

Small update: it's most likely not ECU software related. Found at least one case in US with all the latest OEM software and still failing occasionally - less frequently though.
mil - mine was upgraded to the latest OEM software and the problem still occured. However I replaced everything in the car mechanicals wise (gearbox, SMG pump etc) and it still happened, so I was lost as to what caused it based on my process of elimination.

One thought is that my car had a remap on the main ECU, however I'm pretty sure that was first done at the point of replacing my first gearbox.

Still confused. I hate problems like this that the process of elimination doesn't help. :banghead:

[mil]

Steve,

This is very strange indeed and even more strange is that sometimes new gearbox seems to help. What I found interesting is what you say in the very first post that your problems also started after replacing the clutch. It must be is something related to changed clearances and adapting to that somehow. Also this gearbox temperature is an interesting possibility.

After I got new gearbox it was first making the errors on street only after some maybe 10-20km of driving after cold start, so I don't think the oil temperature was too hot. Last summer I was running on Nurburgring for days without any issues on track, but it was happening on streets around the track. :)

Actually now when I'm more thinking back last summer, the first strange thing with new gearbox after I got SMG software updated was slight delays in 3->4 shifting speed in S4 mode. Started to use to S5 which fixed the delays but eventually that resulted to mechanical noises after couple of days of driving on track... Could it still be somehow related to that damn 5£ spring which fails very quickly in our cars because of some other issue. Maybe this is some sort of chain reaction, which could explain that there are times when this is not happening after make some changes to the system.

[jay959]

Hi,

Shimmy- my views are always expressed from first hand
experince and things that have happened to my cars.

Just for the record, a Lightweiight flywheel [12lbs] with
a Sachs Uprated Clutch Disc and cover was fitted to my Car, CSL.

It was dreadful, so the Gearbox ECU was reprogramed with the
latest version of the software, no change.

Then the SMG pump fluid was drained the system was flushed and
refilled. No change still would not engage properly, the upshifts and
downshifts were all hit or miss etc.

So the Lighter flywheel was removed, the dual mass refitted, with
the Sachs clutch, and the car has its moments but by and large its
OK. Can still get a small 'slur' now and then without sport or DSC off.
Now done around 1500 hard miles, its only used for Track days and the
odd local blast when trying things out, and its been OK.

I also have a E30 M3 with a CSL S54 engine Motec M800 and Drenth sequential Gearbox running a Dual disc 184MM Clutch with a 10lb
alloy flywheel, and a central clutch cylinder, which on the 'flatshit'
makes the SMG feel very slow.
This car does not run the 'E,Gas' or Fly by wire, but is running a throttle
cable/Linkage, which out of slower bends does allow a quicker pick up.
The S54 without the dual mass flywheel is far more responsive at lower revs
that its a shame that the SMG will not function correctly
with a lighter flywheel.

I did look into lighter dual mass flywheel in steel, but the savings
were not more than around 2-3 Kg which was not worth the costs.

Pectel have now developed a plug and play standalone for the S54 which
has been mapped specifically for the E.Gas, fly by wire, and in therory
will always have the throttle and air optimised as its rev matched and
picking up signals from engine load etc.
Interestingly they do not recommend SMG on a Car running this system.

Regards,

The Gorilla.



I run a sachs sintered paddle clutch on a supercharged m3 e46 smg, had a few problems with adaptation but im told by extending the actuator 5mm should solve the problem so its watch this space, when it was running was fine but shut down a couple of times due to this needed mod...waiting for it to come back in as we speak!:thumbs:

[The Gorilla]

Hi,

Jay959- I hope it works, but I have reservations.

The more I learn and read about SMG II the more
I believe that its problems stem from the fact that
the whole system when designed was based on the
principal that the take up point on the clutch would
always be the same distance.

By reason that the SAC system would compensate
for wear.

Thus when the system goes through its shift pattern
the ECU will not allow the upshift until the system
is within the paramiters.

Hence Slip or 'Slur' as it sorts itself out.

When driving the system hard, those paramiters
move up as throttle load, revs etc are all at the top
end, so the ECU is already primed, and hence the
shifts engage quicker but much harder on the drivetrain.

With the added 'adaptive' element for driving styles is
also factored in then Slur or Slip is the result.

On current F1 Cars if they do not take the box up and
down on the first start up of each session then the
system will revert to base 'mode'.

Manual S54 M3's do not suffer
as badly with clutch slip as SMG cars, although
its almost an identical gearbox, clutch/flywheel
is the same, so the logic clearly points to it
being a electrical/software/hydraulic issue, which
as they wear will bring on more and more issues.

Be interested to hear how your modification works out.

Regards,

The Gorilla.

[mil]

My car has been investigated further but still no solution has been found. However I have collected some pieces of new information.

The BMW service has taken the transmission into pieces after car was "online" diagnosed by BMW. First instructions were to check the clutch, flywheel etc. and they seemed to be in really good condition and were not replaced again - at least yet. After that my issue was escalated to Germany, who instructed to remove aftermarket software from ECU. So yes, they can see those mods. :)

Also during the last 12 months yet another update for SMG software has been released. So I got the latest engine and SMG software. Shifting felt smoother, but I obviously cannot tell if that was because of SMG or engine software. Anyway the problem remains, but software can be ruled out now. The saga continues next week, but at least BMW Germany is involved, hopefully they know their products.. :)

[Mark CSL]

My car has been investigated further but still no solution has been found. However I have collected some pieces of new information.

The BMW service has taken the transmission into pieces after car was "online" diagnosed by BMW. First instructions were to check the clutch, flywheel etc. and they seemed to be in really good condition and were not replaced again - at least yet. After that my issue was escalated to Germany, who instructed to remove aftermarket software from ECU. So yes, they can see those mods. :)

Also during the last 12 months yet another update for SMG software has been released. So I got the latest engine and SMG software. Shifting felt smoother, but I obviously cannot tell if that was because of SMG or engine software. Anyway the problem remains, but software can be ruled out now. The saga continues next week, but at least BMW Germany is involved, hopefully they know their products.. :)

Is your car under bmw warranty ? i ask as a friend of mine had his warranty removed as the ecu had been chipped so i find this strange but thats bmw for you good luck with a fix soon :whistle:

[Great Pretender]

Folks,

I've been reading this thread with interest. One thought has occurred to me though:

With all the problems some of you have had in respect to the SMG II, why not convert the car to a manual transmission and solve the problem permanently?

[shimmy]

Folks,

I've been reading this thread with interest. One thought has occurred to me though:

With all the problems some of you have had in respect to the SMG II, why not convert the car to a manual transmission and solve the problem permanently?

No point if warranty covers it but you may find a few do this as warranties expire

trouble is the cost for the change over in new clutch and extra possible loss if value as CSL will be harder to sell outweighs the cost of a clutch alone for tge SMG

most will only have this problem once within their ownership

[DuncanR]

With all the problems some of you have had in respect to the SMG II, why not convert the car to a manual transmission and solve the problem permanently?

Cos it would fook peeps like T$ and Lawsy up a bit !:hahaha:

[Bounce]

Cos it would fook peeps like T$ and Lawsy up a bit !:hahaha::hahaha::hahaha::whistle:

[flow]

I also have the same problem with the 4th gear , some times it will not shift into 4th and makes a grinding noise .

I had my local shop (BMW specialist) change the clutch en those little cheap springs , but the springs were fine . So the springs can't be the problem with my SMG .

After talking to the mecanic and explaing the problem he said that when installing the clutch he had a problem removing this part nr9


http://img.photobucket.com/albums/v226/sgill22/CSL/241.png

He said that normally with a special tool it is easy to remove , but in my box it was pretty much stuck and according to him that is a part that should be able to move .
Before re installing the part he cleand it and put some grease on it so it can move better .
I did a little test drive and now the SMG shifts are alot smoother .
what are your toughts on that ? could that be the problem or A problem ?
This weekend i'm doing a ring day and monday a ring trackday so i can really test if the SMG is OK now .

[mil]

Hi Flow,

Thanks for the input. Anything is possible in this case I think. Please let us know if that will help with your car.

Since my previous post my car has got:
- gear identification switch (strange call as this should be included in the complete gearbox swap earlier)
- rear differential
- output shafts (left and right)
- rear wheel bearings and hubs (a separate problem there, but changed anyway)
- clutch bleeding several times
- all possible reset/adaptations several times

No solution. Next on the line is clutch output cylinder and then.. you guessed it: the smg hydraulic unit.

[flow]

Hi Flow,

Thanks for the input. Anything is possible in this case I think. Please let us know if that will help with your car.

Since my previous post my car has got:
- gear identification switch (strange call as this should be included in the complete gearbox swap earlier)
- rear differential
- output shafts (left and right)
- rear wheel bearings and hubs (a separate problem there, but changed anyway)
- clutch bleeding several times
- all possible reset/adaptations several times

No solution. Next on the line is clutch output cylinder and then.. you guessed it: the smg hydraulic unit.

I will let you know next week .

[flow]

Car shifts very good and smooth , alot better then before but after a good testdrive the 4th gear problem happend again .

Is it a problem with the syncro's in the gearbox ? because its only one gear ??

[mil]

Flow,

Sorry to hear that the problem still exists. I don't think it's synchros, however it could be, as there are few people who say that new gearbox has helped. New gearbox because you cannot get individual inner gearbox parts from BMW. It's also possible that the same 4th gear grinding symptom is caused by two (or even more) different problems.

In my case new gearbox did not help anything. Only after some hundreds of kilometers it failed again. I suspect it is something outside gearbox and clutch, but so far nobody can confirm this.

[shimmy]

O ad 3-4 grinding and missing gear issue in 2008 at 45k miles.

New gearbox solved it. The gearbox oil showed faint signs of the synchro metal BUT my gut feeling was that this was due to the grinding and bit the cause of it.

Good luck.

[The Gorilla]

Hi,

Its worth noting that on the SMG Box
the rod selector is not spring loaded for
obvious reasons.

In a manual box it is and the detent is set to neutural

Hence when the SMG actuator selects a new
gear, any wear or misalingment on
selection will cause hesitant selctions as
the ECU will detect a] resistance, and b]
greater pressure.

As the selector fork then starts to engage and slide
in to the correct position the pressure is reduced
back to normal, and the resistance point has been
passed, so the gear is then slected.

Hesitant selection is another factor of clutch slur.

Small particules of metal will be evident in the
Gearbox oil due to the misalingment rubbing.

This also explains in part why there is no Gearbox
slur upon a Manual Car, which has almost the same
Gearbox and clutch arrangement.

Regards,

The Gorilla.

[TANKSLAPPER]

I agreed with "The Gorilla"

Mine was missing 4th gear over a 6 month period when I was putting the car under load and did nothing about it until the loose actuator broke off completely.

Replaced the broken actuator and worked ever since perfectly.

I even got a specialist gearbox engineer to check it over and they reported that they never seen a box with so little wear for 50,000 miles. :thumbs:

[Thorney]

Good research form members, here well done.

Just to add some positive comment, my old race car (CSL) has been running with SMG for last two seasons without any issues, however we do inspect the gearbox each season. We've had to replace two manual boxes over the same period so if SMG works well it does protect the gb under hard use.

[The Gorilla]

Hi,

Any Gearbox is under its greatest load when the
Clutch is in, not out.

Hence why flat shifting on a sequential gearbox
causes less load into the box than when using the clutch.

This is why SMG gearboxes in regard of the gearsets will
show very little wear as opposed to a Manual box.

The SMG idea is very sound, but it was a work in progess,
that has since moved on to dual clutch engagement etc, and
a whole new set of issues.

Its like all component intense design, usually fantastic
when it all works as it should, and a right pain when
it don't.

Regards,

The Gorilla.

[manos///3]

I have a serious problem in my smg.
On the road everything is ok.
But on track after two laps , when the whole system (engine,gearbox) reaches high temps ,smg starts to shift 3rd to 4th , or 4th to 6th by its self.

I' ve checked everything on GT1 with no results .

I also changed clutch disk ,pressure plate and the smg relay recently. But the problem still remains.

Yesterday I went to my local BMW service dealer and the mechanic saw liquid under the hydlaulic unit.He cleaned the area under the unit and today there is liquid again at the same point. Is this an issue for upshifts?

Any help???

[shane@mbtech]

I have a serious problem in my smg.
On the road everything is ok.
But on track after two laps , when the whole system (engine,gearbox) reaches high temps ,smg starts to shift 3rd to 4th , or 4th to 6th by its self.

I' ve checked everything on GT1 with no results .

I also changed clutch disk ,pressure plate and the smg relay recently. But the problem still remains.

Yesterday I went to my local BMW service dealer and the mechanic saw liquid under the hydlaulic unit.He cleaned the area under the unit and today there is liquid again at the same point. Is this an issue for upshifts?

Any help???


If you are losing fluid it means it's losing hydraulic pressure, which yes will cause problems.

[grumps]

When you say rod selector are you talking about the shaft that the hydraulic actuator connects to ?

[mil]

Hi Flow,

Thanks for the input. Anything is possible in this case I think. Please let us know if that will help with your car.

Since my previous post my car has got:
- gear identification switch (strange call as this should be included in the complete gearbox swap earlier)
- rear differential
- output shafts (left and right)
- rear wheel bearings and hubs (a separate problem there, but changed anyway)
- clutch bleeding several times
- all possible reset/adaptations several times

No solution. Next on the line is clutch output cylinder and then.. you guessed it: the smg hydraulic unit.

Update: my car seems to be finally fixed.

After the previous post I have got new hydraulic unit (pump), another new clutch and new gearbox (warranty replacement). 2nd replacement gearbox changed behavior a little, shifting failures happened only when hot (basically in track conditions), but did not solve it for good.

Per my own request they then changed engine rubber mountings and gearbox mountings (rubber also). After the work mechanic told me that the engine got positioned 10mm higher and surprisingly everything now works. Mountings were not broken in anyway. This is not an expensive job, just two hours and parts needed are cheap also.

So I'm thinking that track driving, especially Nordschleife, affects those mounting rubbers (like any other rubber in suspension) and when it goes over certain threshold, SMG does not function properly and system cannot be calibrated to work properly even with brand new gearbox. You may still need to replace gearbox if situation has gone bad as this grinding noise comes from synchros, but this is my speculation only. If new gearbox does not help, change for the engine mountings before anything else. If you need to pay gearbox change yourself, you may even try mountings before gearbox especially if the car has been driven hard.

I have now driven several thousands without any shifting errors. Of course this can be combination of several things in the end, but in my case engine and gearbox mountings seem to be the final cause. :)

//mil

[mattCSLnut]

Update: my car seems to be finally fixed.

After the previous post I have got new hydraulic unit (pump), another new clutch and new gearbox (warranty replacement). 2nd replacement gearbox changed behavior a little, shifting failures happened only when hot (basically in track conditions), but did not solve it for good.

Per my own request they then changed engine rubber mountings and gearbox mountings (rubber also). After the work mechanic told me that the engine got positioned 10mm higher and surprisingly everything now works. Mountings were not broken in anyway. This is not an expensive job, just two hours and parts needed are cheap also.

So I'm thinking that track driving, especially Nordschleife, affects those mounting rubbers (like any other rubber in suspension) and when it goes over certain threshold, SMG does not function properly and system cannot be calibrated to work properly even with brand new gearbox. You may still need to replace gearbox if situation has gone bad as this grinding noise comes from synchros, but this is my speculation only. If new gearbox does not help, change for the engine mountings before anything else. If you need to pay gearbox change yourself, you may even try mountings before gearbox especially if the car has been driven hard.

I have now driven several thousands without any shifting errors. Of course this can be combination of several things in the end, but in my case engine and gearbox mountings seem to be the final cause. :)

//mil

Interesting read and discovery :thumbs:
How & against what were these measurements of the engine positioning taken, before and after the replacement rubber mounts ? Sounds like good, preventative measures to be taken by a number of enthusiastic :whistle: CSL owners on here.
Thanks for sharing your info. :beer:

[mil]

Interesting read and discovery :thumbs:
How & against what were these measurements of the engine positioning taken, before and after the replacement rubber mounts ? Sounds like good, preventative measures to be taken by a number of enthusiastic :whistle: CSL owners on here.
Thanks for sharing your info. :beer:
Don't know exactly, I would guess that it's just an estimate by the mechanic after he dropped the engine back and not really measured figure.

I spoke about this last year already with Tom Schirmer at the Ring and I think he mentioned that somewhere after 100000km the mountings could need replacement. My problems started at 114k (incl. hundreds of Ring laps) .

//mil

[mattCSLnut]

Don't know exactly, I would guess that it's just an estimate by the mechanic after he dropped the engine back and not really measured figure.

I spoke about this last year already with Tom Schirmer at the Ring and I think he mentioned that somewhere after 100000km the mountings could need replacement. My problems started at 114k (incl. hundreds of Ring laps) .

//mil
I wonder if this engine mount wear could be measured from the engine bay strut brace to a solid part of the engine, like the cylinder head or something similar. Would be interesting to compare the figures of a 20K miles CSL to lets say a 60K+ miles (100K ish kilometres ) CSL with Track history. I don't have these SMG problems (that you've described) on my CSL (as yet) and I have BMW Warranty but I'm way past the 100,000 kilometres mark and have also driven a fair few laps :whistle: at the Ring in the past few years :smokin:
High time for some NEW engine & gear box mounts I thinks :smokin: but I bet they are NOT covered by BMW Warranty on 60K+ miles cars :bigcry: Group buy anyone ? :whistle:

[m3novo]

I am facing the same problem. Check spring and was ok.

how can I diagnose syncro or SMG? Anyone know how to use INPA for this diagnose? I noticed it has a lot of analog parameters that could be helpful.

[shane@mbtech]

I am facing the same problem. Check spring and was ok.

how can I diagnose syncro or SMG? Anyone know how to use INPA for this diagnose? I noticed it has a lot of analog parameters that could be helpful.

which spring did you check?

There are 2 separate ones on the left of the box. One behind a screw out bung, and one behind a press fit plug.

There are also 3 springs under the plastic blanking cover on right of the box.

Some don't know to remove the press fit plug.

I've got one in at the minute and the spring has snapped and wedged under the plunger, the plunger was wedged so would not hold it in gear correctly.

The faults with this were difficult getting 4th gear, and slow to get any gears, especially under hard acceleration. The clutch release bearing has also worn on this and was dragging considerably, not helping matters any at all.

Also worth noting if your car has a thud on gearchange or take up of drive, then the flywheel is probably knackered. This car has a bad thud and upon removal of box the flywheel has about an inch of free play.

[shane@mbtech]

Also worth noting that on GT1, it passed all the tests. I did however notice that whilst running through all the gears on the test it was very noisy selecting gear compared to a good box. And did feel a little slow.

But the computer was picking up no faults. Back to old school diagnosis for these type of faults.