James Bailey

The ONLY 5 speed car I EVER heard about or knew about was one of Mark Andersons race cars with a custom release bearing that pulled too far and too hard on the pressure plate. The fact that the clutch discs float makes it pretty much impossible to preload the crank on a 5 speed a much diffferent system than the automatic . It is one reason why you should limit the amount of time you hold down the clutch pedal should shift into neutral at stop lights since that is when the thrust bearing is being put under stress also is bending the pressure plate.

OBehave

Why does the shaft have to be locked down on both sides anyway? Most driveshafts on rear wheel drive cars use a slip fit spline to spline yoke on the front of the drive shaft and universal joint bolted to the rear flange which allows the shaft to move in and out of the trans tailshaft for suspension travel.Why not use the same principal on the front hub clamp assy?

Tass 928

My first 928, a 79' euro 5 speed , died of thrust bearing failure at only 45k miles.

I sold it with the engine out and bought an S4. That was about 12 years ago and I have been trying to buy that car back ever since. It is still sitting there, pristine and under cover in a garage, with the engine out.

James Bailey

OK that would be TWO

Tass 928

Just my luck that I would be included in this elete group

I did see the block damage with my own eyes...the shop that was working on the car even bought short block from 928 intl. I believe it went with the car when I sold it and is still laying around somewhere.

Tass 928

Jim....re-reading this and something occurs to me. The shop I was using turned out to be kind of a hack joint and has since gone out of business. At one point in the car's history I pulled my clutch and found that they had installed two identical discs (used). Doesn't one disc have a thinner spline? If he had two of the thick ones (not sure, don't remember) then wouldn't that cause the preload on the crank when the clutch was bolted up?

worf928

Where there's a will, there's a way.

Mark Anderson

My .02 is that the early cars do not have enough torque to cause the slippage in the flex plate plus some early cars have the proper torque tube shims and clip. Why Porsche stopped using them is beyond me.

Black Sea RD

Because they couldn't get their mechanics in the field to get the whole pre-load measurements right.

Torque causing slippage is not the only reason TBF happens to 928s, mechanical inabilities by owners or mechanics causes it too. As discussed by Jim and Tass above...

Cheers,
Constantine

Black Sea RD

BTDT. Didn't work well, too much vibration in the 928 driveline and the cost of this system was much more expensive than the Super Clamp.

PM or call for the down and dirty on this.

Kind regards,
Constantine

86'928S MeteorGrey

When Ernst Fuhrman was ousted from Porsche and replaced with Peter Schutz in 1981, it was said Schutz was into cuting costs. After reviving the 911 from product end of life with engineering upgrades, he considered the 928 inferior to the 911. Maybe the clips and shims were deleted by Schutz because he didn't understand what they were suposed to do... It probably helped speed up the assembly line, and that is the bottom line. Schutz was CEO from 81 to 86... He was not a 928 lover... Need I say more?

mj1pate

Yep. You can imagine a disgruntled CEO walking the assembly line, and taking notice of the time taken to install a ten-cent part and putting a stop to that in a hurry. All this incurring no consequence....at least not during his tenure.

Black Sea RD

The Schutz connection might answer this conundrum but from a different angle.

Porsche recognized that installing these parts by their field techs was a problem. Porsche drive line engineers then thought to remove them from the equation, which they did. The Porsche engineers also realized that they should change the front flexplate clamp. However, when the costs involved for R&D to do this was run up the chain of command, back came an answer that the current clamp was fine.

All this is just conjecture of course, but it does seem to explain why they kept the clamp the same when they should have changed it.

Cheers,
Constantine

James Bailey

I still wonder what caused Porsche to change the thrust bearing design in the early 1980s ? What were they trying to FIX with the larger thrust surface ?

Nightfly

See, it's stuff like this that make me wonder why so many people think Porsche engineers are so brilliant.