Wore out my drive shaft

So I was having clutch release issues and after trying all else, I tore it apart. This is what my drive shaft looks like after 4 years of daily driven LS2 power (clutch end):

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Pilot bearing is cherry as are the TT bearings and motor mounts.

What kind of clutch disc are you using?

You got Spec'd

Don't say that. I have one of those. As a matter of fact I have bought two.

Better copy your TT shaft in 300M.

I have the Spec Kevlar disk and Spec (I believe) heavy duty pressure plate (which I really don't like) all from RH as part of their upgraded clutch kit.

What exactly does this mean?

xschop wrote:Better copy your TT shaft in 300M.

Ouch, any idea of what would prevent this (other than keeping the engine stock). Should the TT have been rebuilt, the Pilot bearing replaced, motor mounts changed, ect? Or is this just one thing that comes with the fun?

Looks to me like the disk was not a good match to the splines. You can see the unharmed splines have a plateau at each peak whereas the worn away splines have a pointed peak. The disk splines could be off just a bit and after repeated cycles, just wear away the splines.

XSCHOP......300 moles?

I saw pics from the old RH dictator board just like DVC's and quench hardened my TT shaft right on the car. The Rockwell hardness of the TT shaft is nowhere near what drive axles are today.

xschop wrote:I saw pics from the old RH dictator board just like DVC's and quench hardened my TT shaft right on the car.

Sounds pretty slick!

So, howja do it?

xschop wrote:I saw pics from the old RH dictator board just like DVC's and quench hardened my TT shaft right on the car. The Rockwell hardness of the TT shaft is nowhere near what drive axles are today.

Hmm, good idea. Did you use an acetylene torch? Any idea what the surface temp was? Do you think there will be a problem with stress cracks from the more brittle material?

Does anyone know the material the TT is made of?

It wasn't too hard, just had a fire extinguisher on hand (wife with a garden hose). I simply used a portable MAPP gas and heated the the entire spline area cherry red and then poured OLD-used motor oil on it with a 50/50 mix of diesel. I took a file to it and the splines were not very easy to file on the ends as before (you can test harness this way)

This is not the problem though. The instant torque of the V8 is what is killing the TT shaft tip and the poor design of the swap disc.

Edit: I'm putting a pictorial together to drop some knowledge and why I chose the Specific Dodge Truck Disc. From my drawings looks like DVC's TT spline engagement's about 18-19mm, can't imagine it held this long.

Constantine (same guy who makes the TT bearings) is selling new improved driveshafts for the 944's, i believe.

Porch wrote:Constantine (same guy who makes the TT bearings) is selling new improved driveshafts for the 944's, i believe.

In that case, think he can make one with the stock corvette spline!!

I have a piece of 300M rod sitting around at the shop from months ago. But I believe the clutch disc spline engagement lenth (Lack thereof) IS the problem obviously. I talked with Constantine before about this problem. He would sell out if he made them 2-piece like the 928 manual TT's...especially on a C5 2-piece BH 948.

What's the exact fore to aft spline engagement length?

I have a rebuilt TT coming from Constantine with his Super Bearings. Great guy to deal with! Also a Stage 2 Spec clutch along with their aluminum FW and aluminum PP.

""""Also a Stage 2 Spec clutch along with their aluminum FW and aluminum PP.""""

You'll just fry the new TT 2x as quick if the disc splines are the same length.....

You'll just fry the new TT 2x as quick if the disc splines are the same length.....

I'm not certain that is true. MichaelB has his LS supercharged and routinely drag races it.He hasn't said anything about his TT. I seem to remember ~600 HP at the rear wheels? Also turbo bob with his GN powered 924. I seem to remember he had about the same and all he did was trash transaxles.

Why is your disc only burnt on one side??

You cannot double the power and torque of the 944 drivetrain and decrease the clutch spline engagement and expect the TT shaft tip to last long. Just by looking at the pics of the RH clutches and Spec clutches made me run. I'm glad RH banned me back in the day and didn't get suckered into their SMS engineering lol....clueless

Well, found some more time to look at it. This pic illustrates where the clutch sat when it was engaged.

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If you have a swap built by Mike Gokey, I recommend checking yours.

Constantine just stopped by my house to pick up my old TT (He's going to recycle the outer tube as the shaft is shot).
We discussed the picture of the DVC's worn shaft. I had previously cut the end of my old shaft to use as a clutch alignment tool, so we inserted it in my new clutch plate (its from Las Vegas) and put a marker tape around the splines to indicate depth of spline engagement. We then compared it with DVC's photo.

My opinion (mine alone) is that the shaft was not fully engaged in the clutch plate and also not fully engaged in the pilot bearing. But, it seems strange that the spline wear is even, almost like the splines had been machined to fit a smaller diameter clutch plate.

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I wasn't thinking about the spline engagement, just the TT.

What I did with mine was I tapped the shaft forward until it engaged the clutch hub completely. (approx. 1/4") There was about 1 5/16" engagement in the transaxle coupler originally so now there is about the same in the disc and the coupling. And I made a new dimple in the shaft (at the rear) so the clamping screw can be put back on.


I know that there are a few that had this problem and destroyed the shaft as well. (from the old board) I have a 1/2" thick adapter plate on a stock Chevy bellhousing (6 3/8" depth Gen I) so the shaft isn't quite long enough. The Quicktime bellhousing is 6 3/8" without an adapter (modified for the 944) so it shouldn't be a problem using one of those.

Maybe your adapter is too thick or your shaft is not in the correct location in the tube. They can move over time. The shaft should be (OEM) 49mm +-0.5mm from the transaxle mounting surface bellhousing to the end of the shaft. The manual says to use a plastic mallet to adjust it.