Bill Ball

Sounds like good shop! Maybe I need to take mine there. I have vibration I was certain was rear tire/wheels balance or out of roundness. But 3 different sets of wheels and tires are vibrating above 80, but not always, as it seems to depends on the road surface. I'm guessing a worn suspension bushing but they all look fine and I can't find anything loose.

DanielD

They have a few race cars and exotics that maintain. They are very knowledgeable folks.
The car rides better than it has since I bought it; it a good day at the beach!

danglerb

Could the TC have been bolted up slightly off center?

DanielD

If it was off center you would think it would vibrate the car all the time at the same rate; it didn't. It did it at first only under load and as the miles piled up it became more pronounced and shook the whole car.

blitz928

Daniel, Glad to be of help.

danglerb

Are you going to open up the old TC to see what was wrong?

Randy V

The torque converter - really?

Maybe the torque converter bearing(s)?

There's not much on a torque converter that can fail.

DanielD

No, it was not the bearings, it was the torque converter itself. The bearings were replaced last year by the PO. I have no idea what the failure mode is and won't know because it is going in as a core on an exchange.

The transmission mechanic said that they hang internally and what looks like an "out of balance" condition is really the internals in the converter hanging up during rotation. I have no idea what the insides of a torque converter consist of.

D

Kevin Michael

I would suggest at the sounds of this that you should ask for your old TC back. Unless the one they gave you was new or rebuilt there would be no core charge. I doubt it was the TC causing your issue. Was the car low on power when it was running rough? You need to be sure as you may have spent a lot of money for someone to replace a coil wire, or worse to just plug it back in. It does happen, mine worked it's way out about half way on the driver's bank and it was running badly as you described. BTW I am a porsche shop only and I get cars in all the time that could be diagnosed on the "heavier" side. A 911 customer last week came in with his 3.2 barely running and cutting out and asked if I could look at it. I soon knew what the problem was and when I was about to tell him he said" The guy I usually use said it needed a new DME (computer) and a head temp sensor, as well as the AFM is out of spec. If it needs these things I would like to replace it all. I would like to try you as you are local." I could have made a killing had I had the conscience. But it was just a 19.00 relay and 40.00 later he was out the door with a sound 911. Yes I could have kept his car a couple days cleaned the parts, faked an invoice and made 2500.00 for a relay. The moral here is you gotta be careful with a lot of shops. I'm not accusing your shop, it just sounds a little odd to me. How many of you other 928'ers have had to replce the TC?
Kevin

Randy V

The TC is a simple fluid clutch:

DanielD

The engine was running fine.
The whole car shook at idle, at 1000rpms and there was another vibration around 1900rpms when underway or sitting still in park or neutral. If you were doing 15-20mph at or above idle the car would shudder violently--to the point it was embarassing. You could shift it from park to drive and it would be a bit less, shift it then to reverse and it would go away when sitting still but come back once the car started rolling in reverse.
When looking under the car the whole rear end was shaking even at idle. It was something out of balance or hanging back there that was causing the shakes...
As for myself, I can vouch that the whole transmission/rear axle assembly was out of the car when it was in the shop. I can also say that it has never ridden smoother since I've had it. But nothing beyond that.

Smithmotorworks

Hey Guys

I own Smith Motorworks, the shop that did the repair work.

I have worked on ALOT of Porsches and quite a few 928's . I have owned 3-4 928's even a GTS but I had never seen this before either. The Torque coverter is the last thing I would have thought would have caused this problem.

When Dans car came in the transaxle would shake violently in park . So much so the drive line would move 6-8 inches up and down just at idle. But it ran good, shifted fine amd the torque converter bearing and already been replaced.

The only time I have ever seen this is when the flex plate at the converter seperates and brakes a chunk off , throwing it out of balance badly. That's not a real common problem. But there is a Tech Bulletin from Porsche about the rivets failing and causing this. So This is what I expected to see and even told Dan thats what I thought it might be before we even started.

After we took it apart we found nothing visually wrong. Since I am also not a transmission shop or transmission specialist. I called for some help to be sure this was the problem.

I had a budy of mine come look at it with me, Lucky Eckman, some of you may remember Lucky from Devek . He had never seen this either.

I even had a transmission specialist come to my shop and look at it the converter with me. He said that something did not feel right. He thought that the sprag clutch was trying to lock up and then releasing.

Changing the Torque converter is a 12.5 hrs worth of labor and I damn sure didn't want to take it back apart if that did not fix the car! Thats why I asked Lucky and John(the tranny guy) to give me their oppions too.

So after we checked and eliminated every other possible solution, we changed the torque converter.
As soon as we started the car there was no question it was fixed. No more shaking!

Since Dan was here on vacation , we only had a couple of days to knock this out. A new one from Porsche is $1600. A rebuilt is $450. We opted for the rebuilt option. Thats why there was a core charge. Thats also why we did not cut it open to see what was wrong on the inside of it.

Thanks
Dave

Smithmotorworks

If anyone is interested here's a link about torque converters
http://www.torque-converter.net/

Mrmerlin

Thanks for adding your info Dave, it makes it easier to diagnose future problems

DanielD

Dave really did a great job on the car.

After I arrived home my son (motorhead kid that would love to work at Dave's shop) got in it with me for a short ride and immediately noted it was fixed; he couldn't believe how smooth the car was.
As I said above, it was fixed and it never ran smoother since I've had it.
I guess we all need to put this one on record...

A few more bits here, the car had 121K on it when I bought it. Looking back, there was a vibration in the car then. At 124K it was totally unacceptable and getting noticeably worse; that's when I turned it over to Dave while on vacation in sunny Florida.