Noisy Axles, Is there a trick I don't know about? Options

[John]

This past weekend, I did my first track event of the year (have been doing them for the last 18 years).

I started hearing a clunking noise from the rear. It sounded like it was coming from the Left Rear (Driver side). I checked it out and the only thing I could find was that if you grab the axle shaft and vigerously shake it side to side, the axle shaft will bottom out and cause the clunking sound I am hearing out on the track.

What I believe has happened is that there is no grease left at the end between the stub shaft and the end of the axle to cusion the shaft movement.

Here is part of my problem. I bought the axle shafts from Patrick Motorsports 2-3 years ago when I did the 915/916 transmission, and they are different axle shafts. The stub shaft is connected to the CV joint and the other CV joint (tranny end) has a sealing cap crimped to it. I don't know if it is perminantly attached, or if it comes off.

Are the axle shafts worn out when you can move the axle shaft like this, or do they need grease. If they need grease, how do I get the grease in where I think they need it?

The only changes I made to the rear suspension this winter was to lower it about 3/4" (axle shafts are horizontal), increase the spring rate from 350# to 400#, and align it. I have checked everything out and nothing is loose.

Any ideas, suggestions, or wisecracks welcomed.

[John]

These perticular axles came from Patrick Motorsports.

They were new 2-3 years ago.

They came sealed up and were lubed.

These have a 911 CV joints (to work with the converted 915 gearbox). The outer CV joint is also the stub axle.

When I installed these axles, they came with a spacer that went between the stub axle and the Rear Wheel Bearing. I believe the spacers were about 3/8" thick.

These same axles have been used for the last 2 or 3 seasons of DE events without this clunking issue.

I agree with the idea that now that the ride height is lower, the axles are now effectively longer.

Patrick Motorsports offered to sell me MORE spacers to put in there, but I'm thinking that I may need LESS....


To answer some of the questions...

While the car is up on the lift with the wheels off the ground, there seems to be no binding of the axles as I rotate the wheels. I can set the trailing arms up on blocks (to simulate sitting on the ground) and feel no binding of the CV joints. The only symptom is that the axle shafts can move toward and away from the transmission easier than I believe they should and can "bottom out". I think that when they "bottom out" on the track it is just touching or it would really make a hellofa knock.

This same car ran for years on the track with 914/6 axles and CV joints with no issues.

These are indeed 911 axles (per Patrick Motorsports).

Fuck it. I'm taking the spacers out to see what happens.

(I may have to limit the downward travel of the trailing arms somehow)

Any suggestions? I'll try pulling one out tonight and take a pic......