rexpontius

I took the 928 out for a couple of longer (200 mile +) drives this weekend, and I noticed something strange.

The auto-tranny seems to work fine in all gears when the oil is cold or when driven shorter distances (< 25 miles)

When I have driven longer distances, especially with a lot of highway sections, and I back-up the car into reverse gea, it seems as if the rear wheels are 'blocked' from rolling backwards.

I dont know how best to describe it, but it feels as if there is a ratchet mechanism connected to the rear wheels and the car rolls backward with a noticable "clunk-clunk-clunk" throught the driveline.

This does not occur in the forward gears, only very very mildly in first gear with very low speeds in corners.

When I let the car cool down ~30 mins, all is good and smooth again.
Could it be that my CV-joints are on the way out, or is it more a tranny / LSD (my car has the LSD) issue?

Any help appreciated.

cheers

PorKen

Maybe the gear selector cable is not adjusted properly? Slightly in [P] when the transmission is hot?

rexpontius

Hmm, another good idea Ken :-)
I'll check this week if it helps when I put the selector slightly more towards N.

Cheers
Michel

Tails

+1 to Ken's suggestion.

In addition to checking out the gear selection as per WSM, I would also check the adjustment of the "safety switch" and adjust if required. Again as per WSM.

If this does not solve the noise, then I would check out the CV joints.

The CVs are not necessary worn out, but they need to be removed, cleaned, inspected for wear and or rust etc. If considered OK then repack with grease and while you are in there renew the rubber boots.

On reassemble ensure that the connecting bolts are torqued up to specification ft/lbs.

Dwayne has an excellent write up on CV joints.

Tails 1990 928S$ Auto

rexpontius

Thanks,

Which safety switch do you mean Tails?
The **** on the selector?

cheers
Michel

Leon Speed

Tails probably means the P/N switch which is located under the gear selector.

But that would be weird since it only allows the car to start or not.

rexpontius

I dont suspect the switch, the car starts just fine.

I replaced both boots on the CV's on the right side a couple of weeks ago and they seemed fine. Repacked them with new grease off course, but this r&r did not make any difference with regard to the vibrations.

Could be the left drifeshaft though, I believe it gets quite hot because of the exhaust closeby.
Will check the selector cable first, and will move on to the driveshaft and CV's if the cable is not the culprit

Cheers