[s-cars] Clunking Sound

Sean Douglas quattro20v at telus.net
Sat May 13 15:37:58 EDT 2006

After driving my car for a week now after doing the suspension work, I'm
getting a clunking sound. I drove it pretty gingerly for the first few
days to shake it down, but now I'm confident the suspension is tight so
I've been doing some hard runs.

Under hard acceleration in 1st and 2nd gear, full boost, I hear sort of
a rubbing/grinding sound along with a vibration. Its not a metallic
sound, more of a vibration. This does not happen at anything less than
100% throttle and only in 1st and 2nd. 3rd up, there is no sound or
vibration. In 1st or 2nd gear if I cycle on/off the throttle hard, I get
a loud clunk as if there is some play somewhere in the drivetrain. It
sounds like its coming from the rear and it sounds/feels like it
transmitting through the body.

I'm convinced its to do with the either the driveshaft, rear
differential or rear axles. All of these were apart for my project.

Things related that I replaced were:

- V8 Torsen differential (from a 1990 V8) with new OEM fluid and new
- Used rear axles x2 to replace the outer CV joints I messed up
- new driveshaft bolts

Things I've checked:
- inner CV joint bolts are all tight and torqued
- driveshaft bolts to differential input are tight
- there is considerable play in the V8 differential, I can turn the
input shaft about 10-12 mm before it engages the rear hubs, my stock
diff only allowed about 2 mm of play.

I noticed that when removing the driveshaft, Bentley tells you to mark
the position on the differential input hub. But in my case I was
replacing the differential, so this was not possible.

Could the differential be bad? The play in the differential seems
excessive to me. I guess one way to find out is to put my original
differential back in and see but I really don't want to do this...

Perhaps the driveshaft is bad or center bearing? I don't see how this is
possible as all I did was remove it at the rear end.

Or maybe the rear axle CV joints are worn? I don't think this is likely
either as I've heard they are very stout.



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