Leaking M5 transmission +

[Anthony (M5 in Calgary)]

Hi gang, it's been a while since I've visited this board - so much has changed but there are still some familliar names and cars.

My problems today:

1) 1991 M5 with a leaking transmission. I've been told by others that a common source of leaks is the shift detent cover and that it has been changed to a newer style with better sealing. Anybody have pictures of this cover and/or the fill and drain plugs?

2) The driveshaft makes a "clink" noise during transition between drive and coast and is most audible at parking lot speeds. I suspect the noise comes from the spline behind the center bearing. Any thoughts? Is this joint supposed to be a) greased, b) loctite, c) dry? Any torque spec on the collar nut? The local stealer wants to put in a new shaft at new shaft prices...

Thanks guys, it's nice to be back.

Anthony

[TheGeak]

I have a refurbished shaft for sale, just had all new parts put on too ;) $150 + shiping and its yours :)

[Jr ///M5]

Yes the detent seal has a new design and better sealing. It is located on the drivers side rear section of the transmission, at the 10-11 o'clock position as viewed from the back of the car. It's a small plate that is held on by 2 small bolts that house a couple of springs. If your transmission is "weeping" and you can't seem to pinpoint the leak, it could be the detent seal, shifter shaft seal, top vent, or rear shaft seal. It's possible, but not likely, that the gasket between the two halves of the transmission is leaking. The vent can cause blow off at high rpm, it's located at the top front of the transmission. You won't be able to see it without a mirror, but you can feel it, and check for the "up and down" movement.

It's hard to diagnose a sound on the board. Any work on the driveshaft will mean the exhaust will have to be removed. With it out of the way you will be able to check the heat shield and other items that could be getting in the way because of a worn center bearing. I would change the flex disc and center bearing first. At least you will be able to inspect the shaft for binding operation while it's out and if it needs to be replaced, there are a couple of good remanufacturers to consider using. Just remember to index your driveshaft before pulling it apart or you just might be doing the job again to chase a vibration problem.

Hope this helps some,
Jr
'91 ///M5
'91 318iS
'01 525iA

[Brandon J]

Have you checked if your guibo (flex disc) is cracked? That will yield the clunk b/c the difference in speed of the rear diff and the tranny upon acceleration and lifting off throttle. You might also want to look into the rear subframe bushings. Both are common culprits and wear items.

[Anthony (M5 in Calgary)]

I have a refurbished shaft for sale, just had all new parts put on too ;) $150 + shiping and its yours :)

What's your location? I'm in Calgary Alberta (Great White North)

Cheers,
Anthony

[Anthony (M5 in Calgary)]

Have you checked if your guibo (flex disc) is cracked? That will yield the clunk b/c the difference in speed of the rear diff and the tranny upon acceleration and lifting off throttle. You might also want to look into the rear subframe bushings. Both are common culprits and wear items.

The stealer says the flex disc and center bearing are fine. The noise is a sharp metallic click/clink rather than a heavy clunk. I can re-create the noise by rocking the car in gear, pushing from outside.

After looking at RealOem's site there may be two places for this play: there is a spline at the center support and another at the CV joint at the back end. The one at the front is secured with a bolt and the CV is only secured by a clip.

http://www.realoem.com/bmw/partgrp.do?model=HD93&mospid=47412&prod=19901100&hg=26&fg=10

Cheers,
Anthony

[TheGeak]

i'm near Philadelphia Pa. Just a thought for ya ;)

[Anthony (M5 in Calgary)]

Yes the detent seal has a new design and better sealing. It is located on the drivers side rear section of the transmission, at the 10-11 o'clock position as viewed from the back of the car. It's a small plate that is held on by 2 small bolts that house a couple of springs. If your transmission is "weeping" and you can't seem to pinpoint the leak, it could be the detent seal, shifter shaft seal, top vent, or rear shaft seal. It's possible, but not likely, that the gasket between the two halves of the transmission is leaking. The vent can cause blow off at high rpm, it's located at the top front of the transmission. You won't be able to see it without a mirror, but you can feel it, and check for the "up and down" movement.

It's hard to diagnose a sound on the board. Any work on the driveshaft will mean the exhaust will have to be removed. With it out of the way you will be able to check the heat shield and other items that could be getting in the way because of a worn center bearing. I would change the flex disc and center bearing first. At least you will be able to inspect the shaft for binding operation while it's out and if it needs to be replaced, there are a couple of good remanufacturers to consider using. Just remember to index your driveshaft before pulling it apart or you just might be doing the job again to chase a vibration problem.

Hope this helps some,
Jr
'91 ///M5
'91 318iS
'01 525iA

Yeah, this does help. I'm writing up a parts order for BMA. Hopefully they sell the revised detent cover - if not its to the stealer... As for indexing the DS, I'm an old hand at DS R&R and learned the indexing/phasing lesson early.

Cheers,
Anthony