X5 transmission control module replacement..

[turquise1]

Originally Posted by nigelrfoster

I had the same issue and I had to replace my whole transmission at a cost of £4000. BMW quoted £6750, but I found a few ZF Dealers ( ZF is the gearbox manufacturer)> once the new trans installed they had to reprograme the 2005 X5 to talk to the engine mangement system... a year on and all is going fine... ZF state that X5 auto gearbox are only good for 100,000 miles! I got 114,000 miles out of my first.

Luckily (or not), my transmission was rebuilt only last year, so its still under warranty. What is really annoying is that the transmission guy is trying to avoid going into the tranny itself (other than changing the valve body and speed sensor) for so long and making me pay for all the stuff since they are not covered..

Ozzie

[RRPhil]

Originally Posted by turquise1

Any other ideas before I &^%^& the transmission guy?

A-clutch leakage caused by the axial bearing between the B-clutch hub and the C-clutch drum failing, allowing axial movement of the input shaft assembly within the B-clutch drum, uncovering the O-ring seal between them, causing it to split and provide a leakage path.

Oil pump can keep up with the leakage when the fluid is cold but when fluid becomes warm and less viscous the pump no longer has sufficient flow to maintain clutch pressure and the A-clutch slips and the ECU detects this from the speed sensors and immediately dumps the transmission into failsafe. When the fluid cools down again the transmission performs fine.

A-clutch is used in all forward gears except 5th so ECU engages limp-home (4th gear), still detects slip in A-clutch and has no choice other than to try for 5th. Unlike the A & C clutches which have accumulator circuits for smooth gear engagement from stationary (D & R respectively) 5th gear comes in with a bang.

Reverse uses C & F clutches only so its function is unaffected by the A-clutch leak.

Phil

[turquise1]

So you are saying that its an internal transmission issue. I do agree with you its something internal (although the transmission guy still insisted today that its something electrical) but how do we explain things turning back normal (for a while at least) after I turn the engine off and on?

Ozzie..

[RRPhil]

If it's an A-clutch leak, this is the O-ring seal that fails and the transmission has to be rebuilt to replace it :



If your engine/transmission are at normal operating temperature (i.e. have been running for at least 20 minutes) and you get the failsafe message, key off to reset the ECU, and then restart the engine are you saying that you can then drive off and have no problems for another 30 minutes before the message reappears? If so, it probably isn't the problem I've described above. This issue would only apply if the transmission had to be left to cool before it functioned correctly again.

Phil

[turquise1]

Thanks a lot for all your help, I appreciate it very much.

I dont think I can drive the car for another 30 mins like that, 5 mins max, maybe.

Also, does this condition explain the car downshifting very rough (when hot, right before the trans fail safe actually starts) from gear 2 to 1 right before it comes to stop?

Thanks again,

Ozzie..

[turquise1]

Here is another thing I noticed today.

I drove the car all day today in manual mode with no shifting problems whatsoever.

Any comments?

Ozzie..

[RRPhil]

A-clutch leakage would have given the same issues in manual mode as it would in automatic mode so we can probably rule that out now.

Need to think again .......

Did they tell you what the actual codes were from the diagnostics check?

Phil

[turquise1]

Originally Posted by RRPhil

A-clutch leakage would have given the same issues in manual mode as it would in automatic mode so we can probably rule that out now.

Need to think again .......

Did they tell you what the actual codes were from the diagnostics check?

Phil

P0720 is the obvious (OBDII) one. 059 (Stall Speed) and 049 (Gear Monitoring) from the module..(P0720 would go away after turn off/on)

Also, I think I spoke too soon, I had a minor manual shifting issue after driving all day. Gear would not stay on 1st, coming to a stop and moved all the way upto 5th, but quickly corrected without any other issues. Maybe my transmission needs exorcism?

Ozzie..

[turquise1]

Update : Torque converter is being replaced, I will let you guys know about the result..

Ozzie ..

[RRPhil]

None of the symptoms you’ve described or the DTCs you’ve mentioned indicate a torque converter problem.

They really are keen not to open up your transmission aren’t they?

Phil