dr bob

The "still rolls in park" symptom says that it's something behind the rear of the trans. From the output shaft/pinion gear, through the rest of the diff, either axle shaft, any CV joint.


Diagnosis:

Raise the rear of the car by the trans crossmember and put it on stands. With the trans in park, crawl under one side of the rear and rotate a wheel while holding the other stationary. Does the drive flange on the side of the diff move with the wheel? Is one of the axle shafts broken? You are looking for a wheel moving but not not the drive flange, indicating a failed axle or CV joint. Check both sides of course.

If the drive flanges move wth the wheels, you next need to check the differential. The rear cover on the diff comes off after you drain the oil. Once the cover is off, you can see whether the pinion moves when both wheels are moved in the same direction. The ring gear should move with the wheels, of course. If it doesn't, you may have missed a broken part of the drive flange and the stub shaft part of it that engages the differential. If the pinion moves OK, even with the trans in park, the problem is right at the front of the pinion or pinion shaft, still behind the parking pawl.

The 'scraping' noise that isn't grinding suggests that the left axle is disconnected or broken at the inner flange, and is laying on top of the exhaust plumbing there next to the differential. Makes the noise when the car moves, since the axle is still connected to the wheel. This one would get a first look in step one above, when you'd notice that the drive flange isn't even connected to the axle anymore.

Remember also that the PSD unit does nothing for you when one side of the drive is disabled. A broken axle or a CV joint that comes unbolted (the Nicole syndrome....) causes only one wheel to have drive power. The conventional LSD unit has clutches that are always engaged, while the PSD is 'smart', and doesn't engage unless one rear wheel is spinning more than a bit faster than the other wheels. A broken CV never allows one wheel to spin faster, so the PSD never sees the "problem".

HTH! With luck, it will be something like an axle, or even the bolts in the drive flange fallen out as Nicole experienced. Remember that the torque on those little allen bolts in the flange is something like 60 lbs/ft IIRC. It's a lot tighter than many DIY 'techs' realize. You can reach through from the wheelwell with a long extension or two to make sure you can get them with torque wrench, but too often this step is missed. There's a reason why they are tightened that much.

Jim bailey - 928 International

My prior vote was a hanging chad .... therefore not countable I missed the "rolls in park" on my first read I now agree with Dr Bob CV bolts may have come loose ! That would also be the least expensive fix !

Bill Ball

OK, Matt. I'll be down about 9.

If this is a detached axle, as has happened to Nicole, Wally and others, I would think that would have been obvious, as it was to them when it happened. Snapped axle shaft - well, maybe that would not be as obvious, but you should spot it pretty quickly.

Normy - that's right, Matt thinks the car is rolling in park. If so, the axle is real suspect.

Thanks again for all the excellent ideas, dr bob, H'man, Jim, Wally and everyone who has taken the time to go through the details and try to make sense of it. In terms of probablilities, axles are #1. If the park function still works, then we move the TT or possibly the primary pump and it should be easy to rule out the TT and at least locate this to the device level. If it's not the axle or output of the tranny and not the TT, then tranny (likely primary pump). Nice whodunnit mystery.

hinchcliffe

Sounds like CV joints. Hopefully anyway. Good luck.

Jim bailey - 928 International

Might be a good idea to have 6 of the allen head m10x 50 bolts handy just in case it was the CV bolts, Bill do you have those in your spares kit ?

SharkSkin

I have a set or two of spares if you need them. Devek might be closer though....

edco

Well it’s the Torque Tube, too bad you could not hear Bill response when we pulled the inspection cover

All in all I’m glad to know where I stand. Thanks to everyone here on Rennlist for all your help and suggestions. A BIG thanks to Bill Ball for stopping over and helping me find the problem.

So I’ll order up a replacement TT, Bill and I are going to tackle it in my garage I’ll let you know the date so you can come feel our pain Seriously if anyone wants to stop in and say Hey you would be most welcome.

Thanks again this group is wonderful…

Loaded

be sure to let us know how much you spend putting her back together

Jim bailey - 928 International

Can I vote again ?

Bill Ball

Well, we went through from rear to front. The half shafts were fine. Turning one wheel spun the other, so the diff was OK. Initially we thought park was not working, so that would have been the pinion output, but we verified that, in fact, park was locking the rear wheels. Got the car up on jack stands. I reached up and with one finger spun the torque converter. Uhoh... I could see the rear flexplate turning with the TC, both spinning freely together. That nailed it - it was no longer connected to the TT shaft at some point along the shaft. Popped the bellhousing cover off and peered up into the darkness at the front of the TT and saw what you see above. So, I yelled to Matt, "Get the light and get under here!"

We adjusted the flexplate 3 weeks ago. It moved 2mm and looked like it had never been touched. The photo shows a goodly amount of rust, but I don't remember anything unusual.

I told Matt to get a rebuilt TT with early shaft and the shim retainer mechanism and an ignition monitoring system bypass relay, even though we have no idea if that was tripped when this broke.

I beat the tar out of my car. Other people run around with 400-500HP blowers. How many of them have broken the TT shaft? Matt pulls into the parking lot and "POP!" Bad juju?

Richard S

Matt, sorry to see that. You've only had the car a short time, I hope this doesn't sour your opinion of 928's. Fortunately, you have Bill to help you, and all of us to lend support as well. Let us know when the repair takes place, if I can make it over I'll lend a hand.

Rich

Mongo

Jumpin' Jesus it looks like celery in a food processor!!!

All I had was funky bearings in mine..

For the record, seems like every thread I've come across so far on here relates to torque tubes today....

Jim_H

WOW!!

StevenB

Matt,

At least is was easy to find. I will come by for the repair

Steve B

edco

Hey Jim,

We had given some erroneous info we still had park...

Tell you what you can change your vote over the phone when I call you this afternoon of course that is if you consider my current TT as a core....

Enjoy my photos I'm just glad it's not the transmission, talk to you in a bit