I did my first Driver's Event yesterday at Sebring. WOW it was fun!!! 125 mph on the straights and screaming turns throughout the couse. It was very challenging yet very rewarding. Suncoast PCA held the event and they did a great job. Everything went very smoothly...

...Well, almost everything was smooth. As I drove away from the track at the end of the day, I noticed a lot of noise out of the back left corner of my C4S. I need some help in trouble shooting.

The noise I hear has two components, some mechanical rattling, shaking noise that makes me think of CV joint wear and a squeak that sounds like some unhappy metal on metal. The noise is more prevalent during slowdown, particularly on trailing throttle (versus tranny in neutral). It's there but pretty quiet on acceleration or steady throttle. And it is getting worse (95 mile drive home from the track)!

I've searched the archives and therefore suspect the LSD. Does ANYONE have experience with this type of problem or some good advice to guide my trouble shooting? I'm hoping to put the car on jack stands this evening (but first I must convice the wife this is more important than hosting out of town guests).

I appreciate any input from my fellow RENNLISTERS.

 

I wouldn't think you would be able to hear squeaking of dry metal to metal from a differential, since the casting and oil would dampen out noises like that.

I would, however, check your CV joints closely, as well as the boots etc.

Hope this helps!

 

Chris,

I continued searching through the archives and found a great description, including pictures, of the interior of an LSD unit. From that information I agree with your comment: I doesn't really seem like it would be the LSD.

I'll bet your correct and I have a CV joint problem. Hopefully that won't be too challenging to rebuild. Do you have any experience with CV joints on the Porsches?

Scott

 

Try looking at the cv boots and joints first. The boots deteriorate over time, break, and loose their grease. Once the grease is gone, they can make noises like you describe. If no tears, spin the wheels once on stands and listen for your noise.

 

Try looking at the cv boots and joints first. The boots deteriorate over time, break, and loose their grease. Once the grease is gone, they can make noises like you describe. If no tears, spin the wheels once on stands and listen for your noise.

 

As I found out this weekend when my CV and wheel bearings failed on the left rear, you can jack the rear up and tug on your wheel. If it moves, your CV and/or wheel bearings are dead. While I've had many folk tug on the wheels with the car on the ground to pass tech at autocrosses, I was surprised that, once I had the car back on the ground, I could tug all I wanted on the wheel and there was no obvious play. In the air it was scary how much it moved. I've had torn boots with no symptoms at all (and certainly no noise - I don't think a torn boot on it's own will lead to any noise).

 

Like Tom said, even if the CV boots are not torn, you may still want to remove either the inside joint or the entire shaft assy. to have a look-see.

Grease does centrifuge outward withing the CV boot. Sometimes a boot may look intact, but once you massage it, you'll see cracks or splits.

I keep an eye on mine, but havent had them out of my 993 yet. They are similar to most standard CV joints. Once you have the boot off, you can articulate the joint and remove ***** one by one and have a look (after degreasing) for pitting or overheating. At that point, replacement is necessary.

I am not sure if its less expensive to buy an entire halfshaft assy. or replace just the joints. If the halfshaft itself is reused, it always a good idea to keep the left on the left and the right on the right to keep the halfshaft loading in one direction, same as before.

Not sure if thats overkill, but on open wheel racecars, a driveshaft will fail very quickly if the direction is reversed...