Clutch Plate Splines

[MTstig]

I have a 2002 S, with a 3.6 Flat6 engine with 21,000 miles. At the completion of the rebuild, 2020, a new clutch kit was installed. A few weeks ago I lost drive and had the car towed home. After dropping the transmission and removing the clutch two issues stood out. First, the pilot bearing had disintegrated and secondly, the clutch plate splines were worn to the point that the clutch plate would spin on the transmission input shaft! OK, now I know why I lost drive, but what caused the internal clutch plate splines to wear. The input shaft splines show some wear, but I don't know as to what degree. A new clutch plate seems to have good engagement on the input shaft. Has anyone experienced this phenomenon? What could have caused this issue. Thanks for you help.

[JFP in PA]

Most likely caused by the loss of the pilot bearing, which will allow the input shaft to move off axis, killing the disc's splines.

I would carefully examine the trans input shaft and its bearing inside the trans, if either has a lot of wear or movement, I would replace the input shaft and bearing or you could repeat the process all over again.

[MTstig]

Thanks JFP! Here's a couple of shots of the input shaft

[JFP in PA]

It doesn't look bad, but looks aren't everything; it needs to be measured (micrometer) to see how much it is worn, the spline depth needs to be checked for depth and straightness, and the side to side play of the shaft needs to be checked to see if the bearing in the front of the trans needs replacing. Unfortunately, like a lot of other things, Porsche published very little in the way of specs, so the best way to check everything is to have a competent Porsche gear box rebuilder check it out.

Your only other choice is to replace the input shaft, the throw out bearing housing, the the front bearing in the gearbox.