clunk...clunk...clunk, any guesses?
 

Ok, this is weird. This morning while driving my kid to school, I heard a clunk, clunk, clunk sound coming from the middle rear of the car. The rate increased with the speed of the car, not the engine. It was louder at low speed, the faster but quieter at higher speed. I drove about 2 miles to get back home and park the car, but it stopped after about a minute or 2. So when I pulled her into the garage, she was fine again. I took the 'ol crapper to work today because I did not want to temp the Porsche gods. I think I know what this is, but I wanted to hear other's opinions on this. Any ideas?

clunk clunk clunk sounds like CV joints to me. Are your boots torn or rotted?

Check your c/v joints

That's what I also thought. And it came from the right side, so that's where I'll start.

As far as the boots are concerned, they are perfect. CV joints are one of the few things I have not yet rebuilt. Are there some procedures that can walk me through this? Also, how do you know if you need to replace parts?

Any help here is greatly appreciated, thanks!

It could be a shock, if the cv's are ok

Frog in a blender?

I'd vote CV's, but also check your lug nuts.

Rock in the treads of your tire?

John

hmmm, good thought John. It seemed a little louder than that and closer to the tranny. I'll check that when I get home tonight.

Is there a rebuild kit for these CV joints or do they have to be replaced?

Matt, check your half shaft bolts (where they bolt to the tranny).

Check lugs first as i've made that mistake 3 times and counting. But if it's the cv's, the rebuild kit's are basically cv replacements, which means you'd pull the old one off, put on the new one and grease it up before you close it up.

Any gotchas for removing the axles?

The large axle bolt behind the wheel is torqued very tight, if you don't have access to a impact wrench you can use a loooong breaker bar or take it to the closest shop around have them loosen the nut and then tighten enough to drive it home very carefully.

Matt,

I like the idea of the rock from your general description. I have had the same thing on other vehicles. But I would check all four CV boots. If the boots are bad, the joints may not be. The only way to tell is to disassemble and inspect. Be sure you have a solution to dip the joints into to remove the grease.

I removed the rear wheel and loosened all the bolts at the wheel and transmission. You will need to cycle the wheel and use the parking brake and place the transmission in gear after you rotate them. Once all bolts are loose then you can undo them all. take the bolts off the wheel side first. The axle will then rest on the cars arm/assembly. Then take off the nuts near the transmission. The half shaft is a little heavier than you think it is.

Oh, and I always put wayyyyyyy too much grease back into the CV joints. Don't know if this is correct, but it is the way my father and sister taught me.

Be sure to have a torque wrench and verify the setting for your vehicle. I think it is 36 ft pounds, but please double check. My version of 101 gives the wrong torque value (we all make typeos).

Matt: Do a search on this board for CV's. There is no need to remove the axle stub (large nut) on an SC, only the Carrera has to do that. David says it pretty good. I have a pit and found it easier to jack the car up, remove the wheel, and get to the bolts that way. You probably have 8mm Allen bolts with a 6mm Allen head. Make sure to clean out the Allen heads!!! for maximum grip. Some may have a 12point Allen instead of a 6point. Use Schnorr type washers on re-assembly. Do a search!

Matt.. before you do anything else, PLEASE find/borrow/steal a pair of rear wheels that you can run for a test. You would be amazed at the noise that a flat spotted or otherwise faulty tire can create! Worst case, this test will eliminate one potential source of the problem. Best case, it could save you a lot of work and spendy parts. Don't ask me how I know this....please.

The front bearings will make an awful clunking noise as well, if loose. To me that is a simple one to check....push your rear tire side to side and you should (if loose) hear your front bearings clunking.
Got me twice already.....
Koo

Is this common for the clunking to occur only in 1st gear and while coasting? That's my symtom, not to step on toes here. I have always thought it was the CV joints in my rear right. It's not the tranny (I hope) as I recently had it rebuilt, and the grind continues.

any extra thoughts?
regards,

I had the same symptoms just last weekend. Turned out that two of the four bolts holding the driveshaft to the wheel hub were totally backed out and the other two were merely loose. Scary! I went all around the car after that and found loose bolts on the other side as well. They are internal locking bolts (recessed Allan head) and the torque depends on the halfshaft type your car has. LOBRO shafts require 60ft-lbs and the NADELLA shafts require 34ft-lbs. Not sure what the differences are in the shafts...

CVs first....rear sway bar mounts second.....

Ok, well I'm not going to drive it again until I have a look at her. Funny thing is now it's not doing the noise, but I'm afraid to drive it for fear that what's actually clunking is going to actually break. Four things I will verify: 1) CV joints, 2) wheel bearings, 3) sway bar mounts, and 4) lug nuts (not necessarily in that order). I dont think it's a tire flat spot as it started abruptly and stopped. I also dont think it's a tranny problem since it happends while coasting and increases with road speed, not engine speed.

Did I miss anything?