TastyBacon

I've been trying to kill this noise for two weeks now. '99 Coupe, 135k miles. It's sort of a binding/popping noise that sounds like it's coming from the left rear corner of the car. It's most noticeable when going around a right hand turn fast enough to transfer some weight onto the left side of the car and compress the suspension. Doesn't have to be too fast, 20-30MPH will do it. It will sometimes happen over bumps/humps, or turning left, but it's most repeatable when turning right.

It sounds to me like something in the suspension or drivetrain is binding and popping. I guess it could be in the body too, but I'm not sure where else to look. I don't feel it in the car at all, I just hear it.

Here's what I've eliminated so far:

• It's not the CV axle. Inner boot had a hole in it, so I replaced the whole axle.
• The spindle nut isn't loose. It's brand new, and I just torqued it to 118 ft*lb.
• It's not the axle splines. I lubed them with moly grease before installing the axle.
• It's not the upper ball joint or toe rod end. I inspected them both when I replaced the axle and they're in good shape.
• It's not the shock. The shocks were replaced with new C6 Z51 1k miles ago. The lower bolts were torqued to 107 ft*lb. I rechecked the torque when I had the wheel off and everything was still tight.
• It's not the rear suspension subframe. I checked all the nuts holding that on and they are tight.
• It's not the sway bar end links. They were replaced with Moog Problem Solvers 800 miles ago. The nuts are tight and the links are greased.
• It's not the roof. I lubed the latch, ball studs and seals with dielectric grease.
• It's not the hatch. I lubed the hinges with white lithium grease.
• It's probably not the rear diff. I drained out the nasty old gear oil that was in there and replaced it with Mobil 1 75W-90 LS. Didn't make any difference.

Here's everything that I haven't eliminated yet:

• It could be the lower ball joint. I didn't take the spindle completely off when I replaced the axle, so I didn't get a chance to check the lower ball joint. The boot is in good shape though.
• It could be the wheel spacers. The car has C6 wheels with cheap 5/16" universal spacers. They were put on by the previous owner. I've had the car for a little over a month now, and they didn't make any noise before. The wheels have been on and off multiple times and are always torqued to 100 ft*lb.

Any other ideas? I was sure that one of the things I did above would fix it, and it hasn't. I'm really running out of things to try. I'd appreciate any suggestions you guys can think of! Thanks.

Bill Curlee

Wheel Hub could be going bad. Check for slop/lost motion/ Jack the rear and push pull the wheel at 1200, 0600 and 0300 and 0900 positions., You should see little or no wheel movement in any poaition.

If so,, replace the HUB.

BC

K-n

It's a stretch, but I had a pop in my C6 that I chased for a long time. Checked many similar items in your list. In the end, the tunnel plate was not tight and it was popping when the chassis flexed. It's a free check when you are under there... My popped more frequently and louder over time until I finally had enough and hunted down the culprit.

callie454

Does the noise go away if you lightly apply the brakes? Could be sloppy pad fit, dry (in need of lube) caliper slides, etc.

$$$frumnuttin'

I had the same problem...turned out to be one of the large rear caliper bolts loosened up creating gaposis. It's the one that must be torqued way up to 165 ft/lbs into a blind hole in the caliper. If you find that it is the culprit just put some red loctite on the threads to lock the bolt in because even with the high torque spec there is no way in hell you will be able to stretch an M14 bolt going into a blind hole. It would need a nut on the other side to achieve clamp load.

TastyBacon

Thanks for the ideas so far. I jacked up the right rear yesterday, and noticed that when I did, the left rear popped as it was being compressed. So I am going to put some stands under the rear crossmember and get some help from a friend to watch & listen for the noise while jacking the left rear spindle up with the wheel off. Hopefully we can pinpoint it. I'll look at all the stuff you guys suggested.

lionelhutz

Check the upper control arm mounts. They have ripped off the frame on a few cars.

Check the sway bar end links again. I had one slightly loose and it made a terrible popping noise. And I mean barely loose, like a hard pull with the wrench to turn it another 1/4 turn fixed it.

Check the lower control arm bolts. I doubt it's this but the front one could be slipping in and out on the alignment cam. I doubt it because it would throw the alignment out badly and you'd know it at higher speeds.

Check the sway bar mounts on the cross member. They corrode there and then bind creating a bind then pop/slip condition. Also, the bar on a few cars has broken there. If the sway bars are still stock, throw a set of C6Z51 bars on it. You will love how much better it corners.

TastyBacon

I've seen that. Mine was built 12/98, so hopefully it's early enough not to have that problem. Scary to think about though.

Will do, thanks.

This reminds me of another story about the car. When I got it home after I bought it, I discovered it had a full inch of rear toe-in! The drive home was scary with the bad alignment and blown rear shocks; it hopped sideways over bumps and was really squirrely. The rear tires (luckily they were just crappy old runflats) were shredded in 300 miles! A buddy and I cranked the rear toe adjusters in until it measured zero toe at ride height, then I took it to the shop for new tires and an alignment check. They said the alignment looked fine, everything was now within spec. I can't explain it...

Yeah, the sway bars are starting to rust out around the bushings. I wrapped them with teflon tape as a band-aid for now. The C6 Z51 bars are in my future plans...just gotta get everything else on the car to a point where I can trust it.

jim993

For two years I chased a double pop or crack that seemed to come from the right rear when going over a specific spot in the road on my trip to or from work.

It finally went away when I lowered the two front top hold down brackets at top of the windshield. Two 10 mm bolts each. You have to take the top off and gently pry the trim back to access these bolts.

TastyBacon

lionelhutz wins. Rear lower control arm, driver's side, front bolt was loose. With some help from a friend I was able to re-torque it without turning the cam; now it's nice and tight. Time to check the alignment again...

Thanks everyone!