Interesting Intermittant Problem
 

Hiya.

1983 SC.

Recently on occasion, while driving there is a rather loud clunk/knock sound.

It goes with wheel RPM, but only if the clutch is engaged. Coasting with the clutch out, sound goes away. Speed of clunk increases with wheel rpm.

Oddly, it has only happened 3 times in the last month. It seems if i remember right, they were all wet days, but I cant be 100% sure of that. It then goes away for days on end.

It sure is loud when its there though. There are absolutely no driveability problems when this is happening either, Just the noise.


Any ideas??

You didn't give the year model of your car, nor whether the clunk is coming from the front or the rear...if it's coming from a rear wheel, I'd be interested in seeing the condition of the CV joints (maybe one has either come loose...either on the transmission end or the rear axle nut has backed off... or it has gone "kaput"). If that isn't the problem, perhaps a bad wheel bearing is the culprit or "heaven forbid", you've got a rubber centered clutch coming apart. Good luck....let us know what the "final answer" might be!!

Sorry. I did put year/model (83 sc)

Clunk is coming from the year. Sounds like drivers side, but I cant be 100% sure.

It doesnt sound like a CV joint. Well, at least like CV joints in a FWD car. The clunk is exactly 1 per wheel RPM. I checked the axle shafts and CV boots. The boots are good, and the shafts have a little in/out play when I grab them with my hand, but it all appears OK.


My worst problem is the intermittancy of this issue. I cant reproduce it by trying. It just shows up once in a while, but when its there, its loud!

cv joint noise typically comes and goes.

CVs from FWD cars can be several different designs ... different from Lobros, and the sounds are quite different, too!

All 911s use Lobros from '68 thru '89 ...

Here are a couple of pertinent threads:

http://forums.pelicanparts.com/showthread.php?s=&threadid=86322&highlight=joint+a ssembly

http://forums.pelicanparts.com/showthread.php?s=&threadid=62514&highlight=joint+d isassembly

Had this noise turned out to be my clutch. It has this rubber coupling that cracked and would clunk under the right circumstances.

Well, I hope CV over clutch.


Any ideas on a way to self-diagnose without taking to many things apart?

I was getting my tires changed so when the car tires were off the ground I could roll the tires foward and backwards while in gear. I isolated the noise and found the problems.