Steve Cattaneo

Greg, it’s good for now, but the way you drive you car you will need to check it every week.

PorKen

My flexplate has not moved since (I put in a rear cooler, and got rid of the banjo fittings). Before that, it would move after a week or two of regular driving.

Even after repeated dyno runs to 150mph, and road speeds of 100.

Steve Cattaneo

An engine crank shaft has two thrust bearing surfaces, fore and aft.



If I remember correctly, it’s been a while since I have done a clutch on a 928. The dual mass clutch on a 928 is a pull to release system; the pressure plate is bolted to the flywheel and the flywheel is bolted to the engine crank. The fork / release lever is supported by the bell housing which is bolted to the engine and the release bearing is supported and pulled aft by the fork / release lever, the release bearing is fixed to the pressure plate diaphragm with a snap ring.




When you disengage the clutch the release bearing pulls the pressure plate diaphragm reward, there by pulling the crank shaft with it via the flywheel (which is bolted the pressure plate) against the crank shaft aft thrust bearing, also if the clutch push rod is not adjusted properly this can also disengage the clutch.

Steve Cattaneo

More, relevant reading material.

http://www.kingbearings.com/advantages.html

Steve Cattaneo

Another thought, in 1997 theC5 corvettes were built with a rear mounted Transmission and a differential configuration with a torque tube vary similar to the 928 setup. Chevy has issue a similar 928 transmission, thrust bearing failure caution, torque tube installing bulletin.

I have never seen or heard of any thrust bearing failure in later models corvettes engines. I have one of two Corvettes that I sponsor, sitting in my shop for a transmission, I have never check the crank, tomorrow I will.



http://www.mastertechtrans.com/post/DSC01088%20(2).JPG


http://www.mastertechtrans.com/post/DSC01089%20(2).JPG

FlyingDog

You are correct about how the clutch works, but it's non adjustable on a 928. The only adjustment is preload on the pedal/master with does not directly effect slave travel.

Bill Ball

In fact, Dennis's thrust bearing was more worn on the front face than the rear. Copper was exposed all the way around on the front face.

Vilhuer

As was in my GTS after 10 years of Berlin city driving.

jon928se

When your foot is not on the clutch pedal the clutch assembly exerts no force on the crankshaft assuming the clutch is adjusted properly.

So is it purely the additional clamping force from the bigger springs in the aftermarket clutches that require a bionic left leg to push the clutch pedal down cause the problem?

Doesn't seem right to me.

Vilhuer

There is no adjustment in clutch push rod. If factory did its job right there is very little force applied to fork when clutch is disengaged. Its needed just to keep push rod from falling off from fork. How big this force is can be estimated by releasing clutch slave cylinder mounting bolts.

Black Sea RD

IIRC, this Corvette TBF problem was caused by heat expansion issues after a trans or TT replacement. I believe the tech bullentin called for the car to be run up to temp then allowed to cool off. The front clamping system for the driveshaft was then released and repositioned before being reclamped.

Constantine


[QUOTE=Steve Cattaneo]Another thought, in 1997 theC5 corvettes were built with a rear mounted Transmission and a differential configuration with a torque tube vary similar to the 928 setup. Chevy has issue a similar 928 transmission, thrust bearing failure caution, torque tube installing bulletin.

SharkSkin

This is actually much more difficult than it sounds. Due to normal variations within tolerances, you could expect one thrust bearing to take all of the wear until the crank moves to the point where it touches the second bearing. I don't think I've ever seen more than one thrust bearing in an engine, and I think this is the reason...

SharkSkin

It seems Dennis was pumping something akin to valve grinding compound through the system by the time it quit. I think it was mentioned in another thread that there was a Fram filter on the bypass circuit, to prevent unfiltered oil from getting in the galleys. What P/N Fram? Do you guys have the filters that were on the car when it quit?

heinrich

I follow your real-world results with interest Ken. There is no denying actual results from an intelligent, informed owner such as you.

Bill Ball

It's not a Fram. We have the filter. Yeah, how did all the bearing crap get into the heads as well as everywhere else???