zekgb

Well I pulled out of the driveway this morning in reverse, put it into Drive and no go, with no movement in any other gears. No noises or other sources of warning, just zero movement.

Here's what I've done so far to diagnose:

-TC is spinning when engine is running.
-Fluid is full and does not smell burnt but level does not lower when engine is running. Fluid does not get appreciably warmer even with car running for 15 minutes.
-Jacked the car up and with the engine started the drivers side wheel will turn in forward gears after getting it started with a bit of a nudge, but the passenger side wheel turns much more slowly or not at all and makes a bit of a scraping/binding sound for about 1/3 of a revolution. Both half shaft outer boots are torn all the way through although they still appear have plenty of grease inside.
-No movement in either side in reverse even with a bit of help.
-Disconnected half shafts at differential. Both differential flanges spin up slowly when engine is running and car is in drive but eventually start spinning normally. They turn forward very slowly when car is in neutral or reverse. They do stop in park
-Differential flanges can be turned by hand with car in park and engine off.
-Verified that shift cable is still attached and moving the shift selector at the tranny correctly.

The tranny was out of the car about 10k miles ago to replace TT/TC bearings and since the TC came out with the flex plate I ended up doing the TC seal as well - making sure to lubricate the TC pump bearing upon re-installation.

I know my next step is to drain the fluid and drop the pan (it looked perfectly clean when I did the TT/TC bearing job) but what else should I be looking for? Am I missing anything simple?

Tails

Sounds like a B2 piston brake failure.

Car has reverse gear but no forward gears.

B2 Piston Failure is a known fault with Mercedes Benz 722.3 large pan boxes and MB has developed a modified B2 Piston.

This can be replaced with the Auto box remaining in the car and is relatively simple procedure if you are a relative competent DIYer.

It will require the car to be put on jack stands, removal of pan and cleaning, renewal of oil filter and checking of the B2 brake band clearance and replacement of the auto fluid

Do a search on B2 piston failure and you should find my write up as well as others on the procedure with adjustments.

Quite a few Rennlisters have changed the B2 pistons and they can be obtain from your local MB dealer much cheaper than at the OPC spare parts dept.

Tails 1990 928S4 auto

zekgb

I saw the B2 threads but since I don't have reverse either I thought this would be ruled out.

SeanR

Sounds like the pump has gone kaput to me. If you don't have reverse, the B2 may be out, but you have other issues.

Tails

Thanks for the clarification, on first reading it sounded that you had reverse and then no other gears. If torque converter is rotating at engne RPMs then issues are within auto box, however, it would pay to view the drive shaft from tthe forward flexplate to the aft flexplate and Torque converter for fractures, missing bolts, broken flex plates, failed clamps to confirm all is OK. If all OK then auto box especially as not drop in oil level or heating up of ATF.

Do you have WSM or Jim's Technical CDs? If you have these go to the trouble shooting pages and look for the symptoms that match your problems.

Tails 1990 928S4 Auto

dr bob

For grins, run the engine, and look through the grates under the torque converter and make sure the converter is rolling with the engine. The trans in-and-out sometimes includes missing the rear pinch bolt location. At least you'll be able to isolate the disconnect to either before or after the front of the trans. Guiding symptom is that the fluid level isn't dropping or warming up at all with the engine running.

SMTCapeCod

Seems to be...