Help me diagnose my drivetrain vibration

Ok, I spent a while digging through search results but couldn't find anyone with symptoms like mine.

I have an 04 M6 with a little over 85K miles on it. Daily driven most of it's life. A few runs on the track several years ago. I get on it once in a while but not often.

Starting yesterday and again today during the drive into work, I noticed a vibration coming from what seems like the passenger side rear. I can hear a droning sound when I'm coasting or slowing. It doesn't seem to go away when I'm on the brakes. At about 25 MPH I get a brief noticable vibration that goes away within a second or two, only to be repeated again somewhere between 15 and 20 or so. Again, only for a second.

I've had for a while a noise that might be related but I can't be sure. After putting on poly suspension bushings and not lubricating them since installation, I'd get a pop once in a while when going over rough roads at slow speeds. I thought it was just that the bushings need to be lubed again but now I'm thinking that it could be related to something with the CV shafts or something like that.

What should I check and what should I be looking for to run down this problem?

Check your cv bolts. Its common for them to loosen up and back out.
I have bolt kits on my web site if you need some.
Also check the driveshaft bolts and couplers.

Let me know if you have any questions.

THanks
Chris

Check the metal caseing that holds the cage and bearings on your cv,check for sighns of distortion,also check the bolts.I would check your bolts in the ds as well.If we can help you with anything let us know.

I'll check the bolts. I'd be surprised if they have backed out after that long but stranger things have happened. I'll give the whole CV assembly a once over as well.

Derf, good to see one of the old timers come around. Howzit going?

While you are under there check the differential mounting bolts. I have found them loose before. Also, an ace mechanic friend of mine found that he had a bent shaft from too much wheel hop.

Derf, good to see one of the old timers come around. Howzit going?

I'm survivin. Still trying to catch up after getting laid off last year and having to move for a new job.

While you are under there check the differential mounting bolts. I have found them loose before. Also, an ace mechanic friend of mine found that he had a bent shaft from too much wheel hop.

After my first or second run at the track in 2004, I decided that drag racing wasn't for me. I haven't hopped a wheel pretty much since then. But thanks for the info. I'll spend some serious time under the car probably tonight or tomorrow and see what I can see.

Well, I think I may have found the culprit. As I was inspecting the shafts, I noticed some accumulation on the exhaust pipes. Turns out, one of the pipes was rubbing on the rubber joint between the drive shaft and the differential. The system shifted around a bit when one of the hangars broke and I didn't go back and make sure it was all back in the right alignment when I put the replacement on. :mad:

Now I need a replacement joint.

Well, I think I may have found the culprit. As I was inspecting the shafts, I noticed some accumulation on the exhaust pipes. Turns out, one of the pipes was rubbing on the rubber joint between the drive shaft and the differential. The system shifted around a bit when one of the hangars broke and I didn't go back and make sure it was all back in the right alignment when I put the replacement on. :mad:

Now I need a replacement joint.


Replacement joint as in cv joint? If so the new half shafts will have those but the new ones are larger and stronger.

Thanks
chris

No, the CV joints appear to be in decent shape. All 24 bolts are tight and the cases are not in bad shape. But I'll still swap in the shafts that should be here as soon as the Fedex guy drops by (they said the package is on the truck for delivery today). Better CV joints aren't a bad thing to have.

Here's a pic of the rubber joint that goes between the drive shaft and the differential. The exhaust pipe on the left was rubbing the joint and all of the shaved off rubber accumulated on the pipe on the right. I have since adjusted the left side pipe back to where it is supposed to be.

http://www.ls1gto.com/forums/attachment.php?attachmentid=111605&d=1250965049

I'm sure that joint will hold up fine for a little while but I'm going to want to replace it sooner or later.

Yea, I'm sure it will fine. I have just what you need to replace that OEM shaft :)

Yea, I'm sure it will fine. I have just what you need to replace that OEM shaft :)

When the budget allows...


But for now it appears that the noise and vibration are completely gone.

I haven't installed new shafts yet.

I'm still getting a popping noise whenever I go over an imperfection in the road or otherwise articulate the suspension. I still think this could be poly bushings in need of some lube but it also could be a CV joint not liking it as well. I'll get everything installed soon and see what happens.

Well, the poly sway bar bushings were pretty solidly stuck in the arms with not a hint of grease remaining on them. A cleaning with some fresh synthetic grease and a tightening of a loose nut on one of the ends and the popping is now gone. It's amazing what some fundamental basic maintenance can accomplish. :doh: