Side to Side Play at CV/Diff??

[IB635]

Greetings gents,
I'm trying to track down my annoying clunk in the rear and I think I've pinned it down to the axle shafts having some play at the flange where it meets the differential. I hear the clunk most clearly as I roll out of the driveway and the wheels individually make the little drop into the gutter, clunk clunk.. The side to side (toward/from wheel/diff) movement of the shaft seems to be normal as needed for travel up and down, however the side to side at the flange seems weird, but it's similar on both sides. Other than that, the shafts and joints feel solid. I've already replaced the subframe bushings, spring mounts, diff mount, etc when I had the subframe off, so I don't think it's the culprit. Is this normal or do I need to be looking at a diff rebuild? Thanks.

http://www.bimmerforums.com/forum/attachment.php?attachmentid=530550&stc=1

[RSheiman]

I believe that's ok. Did you do the sway bar bushings.... also the three 14mm bolts at each shock tower are tight....and your exhaust looks newish so nothing there...and the brake calipers are tight..and if you have lowering springs, is there some spring tension so the hat and spring don't slam on each other ?

[IB635]

RSheiman, Thanks for getting back to me. I've replaced the shock mounts fairly recently, and I've checked the nuts previously as the clunk has been driving me kind of crazy, so that was a first check. Exhaust is new (as in like I just put the cat back in after waiting for 2 months for a warranty replacement and various parts, new-ish cat back), sway bar bushings replaced (but I'll check those again), brake rotors/pads replaced recently and seem to be good-to-go. No lowering springs, replacement BMW stock. The clunk is fairly distinct, and it seems to happen as each wheel/shaft hits the bump or dip, so it seems to be in the movement of the shaft. I wish I could stick my head under there while I pulled out of the driveway, but no go. Would wheel bearings give some sort of sign other than a high pitched squeal? That's the problem with restorations, the more you replace, the more you notice that needs replacing..

[RSheiman]

Can you get some heavy sole to bounce the car to reproduce the noise (is it the car on the way down or on the way back up)? Sway bar links are good also??, axles are original and not rebuilt????? as I have seen such rebuilt crap out there. Also check heat shields on the exhaust for clearance. A lot of people ignore the caliper bushings but they can go and cause a doink as I have personally seen. If you have Bilsteins, which type Sport or HD and what perch are they set on? This is not a bearing issue. I feel your pain.

[IB635]

Thanks for getting back to me. I think the axles are original, but as I was under there trying to replicate the sound, it occurred to me that it seems like the axle shafts move pretty easily side to side and fit the clunk sound to a Tee. I don't feel any play in them forward to rear or up and down, so I don't think the CV joints are bad, but I've looked at CV joint rebuild kits which require repacking the joints with grease, which got me to thinking that perhaps the joint ends are low on grease and allowing the shafts to move too easily?? The shaft ends look easy enough to open up, but I've never gone there yet. Is it just a matter of taking the ends off, and repacking and re-sealing?

[RSheiman]

The up and down motion will cause little axle motion from side to side. I don't think that is the issue. I can move the axles on my e24's, my Bavaria and my Acura from side to side, no motion in the other two planes. They are built this way.

The nuts in the shock tower are tight, but is the nut for the actual strut tightened down? The hat needs to abut the shelf of the shock shaft so there is no motion between them.

BTW: I envy the cleanliness of the underside of you car.

[Bert Poliakoff]

Look at the differential mount. That or a bad guibo can cause a clunk

[RSheiman]

Bert, Diff mount is new. Why would the guibo cause issues in the back?

[IB635]

Thanks guys. Diff mount is new, but I haven't replaced the Quibo yet.

So, after getting under the back end and doing push-ups, pull-ups and various cramped muscle pulling exercises to get the clunk to appear, it seems like it's coming from where the outer CV attaches to the trailing arm at the hub. There's a bit of play in the CV there, when I have the wheel off and just hold the axle shaft with one hand and try to move the rotor with the other, it gives a little front to back, meaning the rotor side moves a little, while the shaft side stays still. But I'm not sure if that should have any slop in it, if not, then it may be the culprit. I'm thinking of just doing a rebuild on them to get that off the list. Thoughts? Thanks!

[Bert Poliakoff]

Look at the differential mount. That or a bad guibo can cause a clunk

Just a swag... scientific wild ass guess,but sound can travel with sympathetic harmonics and can make diagnosing a problem bizarre.

[RSheiman]

Sympathetic Harmonics.....group from the 50's?