Inconsistent SMG Clutch Operation

[flgman1966]

I am working, slowly but surely through some issues with my 2002 M3 Vert with SMG. Currently I am struggling with inconsistent clutch operation. I am mostly referring to departing from a stop, also applies to stop and go traffic. When taking off from a stop I am experiencing inconsistent Clutch Operation. Sometimes it is smooth as butter. The clutch slowly makes contact and there is a smooth transition from a disengaged status to a fully engaged status. Other times the clutch is hitting so very hard. I am imagining that this is vacuum actuated, but I am not sure. It is crazy how different the launches can be, with same gas pedal usage. Can someone tell me if this transition is managed by vacuum? If not vacuum, what is managing the clutch slippage? Within 10000 miles the Guibo and Rear Differential Cover, and bushings, were replaced at the dealer.
I have tried the soft reset. I have INPA. I have OBD II.

[maw1124]

Have you reset adaptations and swapped fluid? That might give your clutch slave a break. Others may have responses as well but this is a heavy 6MT crowd, so their answer is likely to be "convert to 6MT".

maw

[eacmen]

I am working, slowly but surely through some issues with my 2002 M3 Vert with SMG. Currently I am struggling with inconsistent clutch operation. I am mostly referring to departing from a stop, also applies to stop and go traffic. When taking off from a stop I am experiencing inconsistent Clutch Operation. Sometimes it is smooth as butter. The clutch slowly makes contact and there is a smooth transition from a disengaged status to a fully engaged status. Other times the clutch is hitting so very hard. I am imagining that this is vacuum actuated, but I am not sure. It is crazy how different the launches can be, with same gas pedal usage. Can someone tell me if this transition is managed by vacuum? If not vacuum, what is managing the clutch slippage? Within 10000 miles the Guibo and Rear Differential Cover, and bushings, were replaced at the dealer.
I have tried the soft reset. I have INPA. I have OBD II.

The clutch is hydraulically operated by the smg pump not vacuum.

How many miles on the clutch?

[chalaka]

Might be pressure/leaking related issue.. mine's completely shot at this moment.. been parked for like couple months already until i get time to take apart the pump.

before:
i have experienced similar issue as yours.. took off weird, slow engagement sometimes ..
then car starts to drop out of gear, error codes ..cog lights ...took to shop, replaced with used GPS (along with the metal arm---> for controlling the selector things)

car runs fine for a while without dropping gear, but still slow engagement sometimes...then i thought it's "alignment, adaptation" issues..
so i tried the adaptation process with ISTA+, then pump(or something) was making loud whistle / hissing noise during the process ..

after:
car drops out to neutral, cruise for a while, then pops back to gear .. then repeat itself .. can't hold gears .. so i suspect it's the pressure accumulator on mine that was busted .. (or somewhere is having a leak)

[flgman1966]

Thank you for the input!! I have seen that so many quickly go for the conversion. I have toiled over this option, but I think I feel that the car came with the SMG and should remain SMG. Besides, I didn't hate the SMG, like others seem to. As for the miles. I bought with 89k miles, about 7 years ago. Now have about 104k. No idea if clutch/fly wheel were ever replaced. Previously I had an immobilizer issue that I thought was an SMG issue, and I replaced salmon relay. The Immobilizer issue seems to have been within the key. Received 2 keys with car, but one was dead. I never used that key. When starting vehicle became an issue I tried the dead key and problem went away. So replaced key battery and use the dead, now alive, key. Also had to replace TPS's, all three, and the Starter, so in the process the SMG fluid was revitalized, maybe not completely replaced. I also replaced the salmon relay. I guess the other little detail was the instrument cluster died, sent it out to be revitalized. Oh, and so when I thought SMG was an issue with starting vehicle I did the adaptions, a few times. At the time it seemed to help in getting car started. Now I believe it was all within the "bad" key.

[IMOLA3]

Had similar issues and eventually started seeing the cog light on the dash. A new slave cylinder (21522229841) fixed that particular issue for me. Also, don't know how many miles you have, but if you've never replaced the clutch and all associated parts (the main culprit that triggered my clutch change was a busted throwout bearing), you might be due.

[flgman1966]

Oh and yes, yellow cog is illuminated. I do also occasionally get a louder than normal clunk when I put the ignition key in. This is as the transmission is preparing for ignition, I presume when it is moving into neutral. Will look into slave cylinder. Any codes for slave cylinder? Or way to check?

[IMOLA3]

Oh and yes, yellow cog is illuminated. I do also occasionally get a louder than normal clunk when I put the ignition key in. This is as the transmission is preparing for ignition, I presume when it is moving into neutral. Will look into slave cylinder. Any codes for slave cylinder? Or way to check?

I had no codes...just the cog light. Its a relatively easy install...a couple of bolts and removing/re-attaching the hydraulic line. Just have to run the INPA bleed procedure again afterward.

If you don't want to spend a lot on a brand new unit, look on ebay for a used one that looks as clean as possible (nylon tip still rounded/proper color with lowest miles). I picked one up there for $50 and its been working great for 3 years. If you replace the slave for a relatively cheap cost, you'll at least know if its the issue before having to open up the transmission, etc. Just make sure you look for the SMG slave as it is different than the one on the standard 6 speed.

Obviously I don't know if this is your exact issue, but wanted to leave some info here for anyone that might run into similar symptoms down the road.

[sapote]

I do also occasionally get a louder than normal clunk when I put the ignition key in. This is as the transmission is preparing for ignition,

Was it parked in neutral or in gear? If it was in gear then inserting the ignition key should not cause the computer to disengage the clutch automatically (pressurize the slave cylinder); the driver has to shift to neutral or the engine will not crank.

[Arith2]

Was it parked in neutral or in gear? If it was in gear then inserting the ignition key should not cause the computer to disengage the clutch automatically (pressurize the slave cylinder); the driver has to shift to neutral or the engine will not crank.

This can be a great anti theft feature.

My SMG only shifts hard predictably. It's after a hard drive the last key cycle. If I start it, turn it off, and turn it on, it shifts normal. Also, after three or four shifts, it smooths out well. There is nothing intermittent nor a cog light.

[JayVee]

Mine had an issue where it felt like a slipping clutch. I had the car serviced, the clutch is hanging on my wall in front of me at about 50% life. After looking over the parts, the Slave cylinder was to blame as the tip became worn. I'm glad the whole job was done with a new clutch, cylinder, bearings, rear main seal. guibo, csb, fork and pivot pin. You can likely get away with a new slave cylinder but the whole system should really be serviced whole.

[sapote]

Mine had an issue where it felt like a slipping clutch. I had the car serviced, the clutch is hanging on my wall in front of me at about 50% life. After looking over the parts, the Slave cylinder was to blame as the tip became worn. I'm glad the whole job was done with a new clutch, cylinder, bearings, rear main seal. guibo, csb, fork and pivot pin. You can likely get away with a new slave cylinder but the whole system should really be serviced whole.

If the slave pushrod is shortened then clutch should have issue of not disengagement instead of slipping.
In this case I wonder try to relearn the computer might solve the problem as this teaches the computer the new worn slave rod position.

[JayVee]

If the slave pushrod is shortened then clutch should have issue of not disengagement instead of slipping.
In this case I wonder try to relearn the computer might solve the problem as this teaches the computer the new worn slave rod position.

It felt like a worn clutch when shifting and would slip out of first. All other gears grabbed fine, even under torque. This was the main reason I did not suspect a worn clutch.
I believe the worn slave cylinder tip caused the position sensor to provide a faulty signal, messing with the other two linear actuators. A soft-software reset (holding back both paddles above 40mph in neutral) solved the issue but only briefly. I also had the adaptations reset during a re-learn before I did the clutch job.

[flgman1966]

Again, thank you for all the input. I just directed everything you provided and took a couple of things into consideration. After I replaced the starter and took it out for a drive I had trouble with the transmission. When I checked theSMG reservoir it was a little low. So, remembering this I decided to go through the adaption process with INPA. The first step is attach a battery charger. Next step is to Bleed Actuator. I had to do this step about 3 times. The first 2 times I got an error, I didn't note the error. The third, and all subsequent times, it completed successfully. Then I Bled the Clutch. This completed successfully the first time. When I got to the Adaption I got an error every time. I went to the error code area for SMG transmission. I got error 81, estate. I cleared the error. I tried adaption again, and got the error again, I then noticed that in the error notice from the adaption failure I got the same error. Error 81, estate. I checked the SMG errors and only error 81. I am guessing that this is the State of something that is not right. Maybe a Great Position Sensor. Anyone know if I am on the right track?

[sapote]

I went to the error code area for SMG transmission. I got error 81, estate.

Don't know if 81 Decimal or Hex. If Hex 81 then the code points to a bad serial CAN bus between SMG computer and DME. Check the connectors pins and wires for these CAN two signals.

Since the same CAN bus wires are connecting to many module, including the EWS, and so if the engine can start and run, then it is not a general bus signals shorted or opened, but more like locally at the SMG computer connector, pins, wires.