Bill Ball

Dave: You are the man with a plan. We can pop the lower bellhousing cover off in just a minute as I left the rear bolts out when Matt was over a few weeks ago (no need to drop the front exhaust). Thanks for reminding me about the rear TT inspection hole.

Thanks everyone for all the input. We should figure this out in the morning. If Matt's TT shaft snapped while crusing into the parking lot, then the mine must be living on borrowed time. BTW, I had the ignition monitoring system trip on my 89 for no reason 3 times over a month period last year after never tripping before. I disabled it. I know what it is there for, but I expect I would notice a loss of power from ignition failure without this system.

daveo90s4

Hi Nicole,

Thanks for that correction, Don't understand why the PSD put all the power to one side and keep you going, but I don't doubt what you say for a minute.

So Matt, maybe an axle / major CV joint failure is a possibility. Have you checked the back seat for any greasy bit sof axle :-)

Cheers

Dave

Nicole

I believe the PSD is mechanically an open differential that is regulated by the ABS sensors. If those don't signal slip, the differential is open, and the car won't move with just one axle.

Tails

TROUBLE SHOOTING THE PROBLEM.

Automatic Transmission

WSM states on page 38-113

Condition:
No power flow in all selector levers positions for a brief period immediately after starting engine (especially when car has not been used for a while)

Cause/Correction
Torque converter drains partially via leaky or defective lubricating ring on drive shaft or via leaky lubricating valve in shift valve housing.

1. Check lubricating ring on drive shaft, replace if necessary.

2. Check and clean lubricating valve in shift valve housing


Condition:
After installation, transmission has no power flow or fails after a brief time of operation

Torque converter not installed according to instructions. Drive dogs do not engage accurately in drive gear of primary pump

Follow up damage: Torque converter drive dogs and primary pump destroyed.

Replace primary pump and if necessary torque converter,

Correction:
Install torque converter according to instructions.

If it is the torque converter and primary pump I would suggest not to run the engine until inspected and ascertained that all is in order.

If the car’s rear wheels move whilst gear lever is in “P” then there is the possibility of some different problems. To trouble shoot these possible problems I would suggest the following checks:

1. Check gear selector lever in the cabin is still connected to and operating the range selector lever on the left side of the transmission and that the selector positions match. If all OK then proceed to next step.
2. Check the Parking lock operation. The parking lock is effective by way of a pawl when the selector lever is moved to “P”. The AT output shaft drives the transaxle differential drive pinion, so if the parking pawl is operating correctly it will lock the drive shaft and the rear wheels can no longer turn.
3. To check the correct operation of the parking lock, first check the rear wheel drive shaft to see whether all is in order. By starting from the rear (aft) check that the rear wheel drive shafts have no missing bolts, broken drive shafts or broken constant velocity joints. If all in order proceed to next step.
4. With gear box selector in “P”, check to see if the rear wheels can be rotated together either forward or in reverses by hand, if the car is lifted, or if the car is on the ground can it be moved manually forward of aft. If the car can be moved then the parking pawl may have failed or the output drive shaft to the differential drive pinion may have failed. This would require a gear box and transaxle removal and strip down to determine the fault
5. NOTE: Cars fitted with a PSD system needs the engine to be rotating with the aft wheels in the forward direction to allow the system to sense any slippage of either wheel to activate the diff locking mechanism. Therefore the PSD can be ignored in these checks. If the engine is stopped and the rear wheels are lifted clear of the ground the differential will operate like any ordinary vehicle, that is, if the LH rear wheel is rotated forward the RH wheel should rotate in reverse. This contra-rotation will happen when gear box is in “P”, however if the parking pawl has failed both wheels may rotate in the same direction. To do a proper check both wheels need to be rotated in the forward direction to produce a rotating torque on the output shaft to successfully check the parking pawl

If all of the above checks are in order, proven by the rear wheels are successfully locked in “P”, then the next check is to see whether the TT drive train shaft is OK by the following checks.

1. Check torque converter rotation. One method, if the car is still on the ground would be to get a torch and mirror, adjust the mirror to view the torque converter through its lower cover grill, start the car and see whether the torque converter is rotating. Only do this if you consider it safe to start the car and that no further damage can happen. If not rotating then something forward of the torque converter could be the trouble.
2. At this stage I would jack the car up forward and aft, so access can be gained to full drive train from flywheel to transaxle, rear wheel drive shafts. Remember to ensure your car is safely secured with jack stands etc.
3. Again check the torque converter rotation with the engine running and car in “P”. If not rotating move on to next check.
4. Remove exhaust heat shields from around AT, remove rubber bung to expose the aft flexplate clamp. If clamp set bolt is OK and tight and all appears to be OK restart the engine and check the exposed drive shaft, clamp and torque converter for rotation. If not rotating move to next step.
5. Remove rubber bung from bottom of forward flywheel bell housing. The best way to view the forward end of shaft, flexplate clamp and flexplate is to make a 12 volt light probe. The globe can be soldered to a twin core cable and connected to a battery and can be inserted through the bung hole to get a good view of shaft, clamp and flexplate. If all is in order restart engine and check for rotation of flexplate and flywheel. If all is rotating then is would be reasonable to assume a failed torque tube drive shaft.
6. If torque converter , TT drive shaft and forward drive shaft is rotating then the problem is back in the AT box or the transaxle as described in WSM automatic transmission trouble shooting as above of between the flywheel and the crankshaft.

Hope that this helps and please, E&OA.

Tails 1990 928 S4 auto

Bill Ball

Tails: Thanks. I had read the first part of that in the WSM. Matt's failure is to the point where nothing happens, so the primary pump sounds gone, if it is not the TT. You reminded me that the rear TT inspection is hidden by the exhaust and shields. But we can see the TC without removing anything. If it is not rotating the we know the problem is forward. We should have fun in a few hours.

Bill Ball

Matt: The weather forecast has taken a nosedive. It's raining pretty hard and could be raining too much to work on this outside. We may want to hold off.

Normy

Pump failure? If the car still rolls in P I suspect that the failure is something after the transmission. Doesn't putting the car in park manually engage a parking lock pin? I used to park my Jetta in Brussels with the tranny in "N" and set the parking brake so that when people there "park by feel" that my locking pin wouldn't wind up snapped off!

Maybe something in the ring/pinion system broke. Best of luck...

N-

edco

Bill,

We can always push her into the garage it's up to you... let me know

heinrich

Tim a later torque tube is also needed.

AO

Recently, I was surfing some of the 928 pages on the web (unfortunately I can remember where I saw it) but there was a writeup on a shattered shaft in the TT. Pretty nasty stuff. Maybe someone here knows what I'm talking about. Anyway, hoping the best for you.

WallyP

I would bet money on a disconnected axle shaft...

Mark Anderson

My vote is on the torque tube.

Tony

Most common occurance from that system is snapping torque tubes i believe.
Something to do with the unbalanced firing of cylindersor the likes.

Jim bailey - 928 International

I also vote broken drive shaft... have seen several.

IcemanG17

Total bummer to a new 928 owner!!! Hopefully its not to pricey to fix....I vote for driveshaft...sense that is probably the cheapest-easiest to fix!