Liquid1

At Mid-Ohio for the past two days and am getting a rapid knocking sound from the rear in what I suspected was the traction control. It is a fairly rapid knocking sound from the right rear when the car is under high lateral load and beginning to add power as I track out. I shut off the traction control (still leaving active handling on) and am still getting the noise. There is no active handling message that comes up on the DIC. The noise disappears when the car gets settled on the straight, no problems on turn in and doesn't reappear until I start adding power after the apex.

It is a stock 2008 Z06 running Michelin PS2 ZP rubber in the stock sizes. It has been suggested to perhap checkall the bolts on the suspension. Anyone confirm what this is or have any other ideas on what it might be? Thanks!

Liquid1

Also lugs are tight and checked every session.

fatbillybob

Cv joint axle? Check runout

Liquid1

Just went out again and it seems to be increasing. Coming from the right rear only and particularly in right handed corners. Worse when the car is comparatively unloaded, although it occurs even when the suspension is loaded. I'm thinking maybe the right rear wheel bearing going bad? Seems very unusual for a car with less than 10k miles though, even if there are a handful of track days in there.

Z11409

Check axle nut-and make sure caliper bracket is tight also

Liquid1

So we checked all of the suspension bolts on the right rear and everything looks perfect. Caliper is on tight and the boots are solid. A couple pther sillier things I'm brainstorming it might be:

-Something with the LSD?
-Wheel bearing going bad?
-Harness bar binding on the hole cut into the side interior piece (doesn't sound like it is coming from this high up)
-Battery cover bouncing up and down (why would it only be an issue under right turn accelerations?)
-One of the other interior parts binding on another (seems unlikely but they were removed to install the harness bar)

KY-Traveler

Check Wheel bearing. I had this happen and it was the wheel hitting the brake caliper.

VGLNTE1

check the TQ on the sway bar as well...those will pop and creak

Liquid1

There is a service bulletin #07-04-20-002B: Rear Axle Noise or Vibration when Making Turns or Under Hard Acceleration for 2005-2008 Corvettes and 2006-2008 Z06's. It recommends replacement of the rear axle fluid and replacement with a different fluid that contains a limited slip friction modifier for 2007-2008 Z06's. For 2006 Z06's and 2005-2008 Corvettes, if the noise persists, the bulletin recommends subsequent replacement of the posi-traction plates with apparently different plates (not applicable for me since I have an '08 Z).

I will let you all know if this successfully addresses the problem.

Liquid1

Also forgot to add that the dealer checked the wheel bearings and they looked good so that shouldn't be the issue. I tested a little bit on the freeway onramp (it's obviously no track so it isn't a great comparison but was not able to replicate the noise yet. I'll update the thread after I go to the track next, which may be several months.

fastrash

Check your frame crossmember just behind your mufflers - as your exhaust heats up, the exhaust ssystem expands and its the mufflers bouncing against the crossmember. Should be able to see some marks roughly in the shape of the muffler housing (outside rim of housing). My 06 Z06 does the same thing when I have it out on track.

95jersey

I have an aftermarket exhaust and it unfortunately constantly bangs against the crossmemeber.

Liquid1

This was not a constant noise. It occurred only in very specific situations, hard right handed corners when I was at least on maintenence throttle or more.

RagingGrandpa

In any case, I'd have someone put a 160# torque wrench on the axle nuts...

Olitho

Check for cracks on your wheels, specifically the spokes.

I have cracked wheels before and under load the hairline fractures open and close with a fast clicking sound that varies with your speed and it only happens under load.


Oli

ipuig

I had similar symptoms that would manifest themselves periodically while on the street and were most severe when under the conditions you describe.
My problem ended up being worn rear sway bar bushings, they were allowing the sway bar end links to knock against the RR lower control arm. I've replaced the bushings and have experienced no more knocking.

fastrash

I still suggest checking your muffler area and see if its the muffler banging on the crossmemeber. You mention very specific situations - right hand corners which make me think it could be just that. I have the same thing going on at Mid OH. Its and easy check - worth looking before you go looking at the other suggstions. Might save some time.

davidfarmer

check your shocks, upper mounts specifically. You could not "feel" anything right, just the sound???

UstaB-GS549

I have experienced track turds being picked up by the tires and flinging off into the wheel wells. It only happens in one turn when accelerating out of the corner. It also only happens at GingerMan Raceway on evening test and tune nights.

I'm not sure if the rubber is hitting fender liner or muffler, but the noise sounded like something major was broken.

Liquid1

That is correct.