Rapid Knocking from Rear Under Hard Cornering/Acceleration
#1
Instructor
Thread Starter
Rapid Knocking from Rear Under Hard Cornering/Acceleration
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!
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!
#4
Instructor
Thread Starter
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.
#5
Melting Slicks
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.
#6
Instructor
Thread Starter
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)
-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)
#9
Instructor
Thread Starter
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.
I will let you all know if this successfully addresses the problem.
#10
Instructor
Thread Starter
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.
#11
Instructor
Member Since: Aug 2008
Location: Cincinnati Ohio
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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.
Last edited by fastrash; 05-31-2011 at 12:27 PM.
#12
Le Mans Master
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.
#14
In any case, I'd have someone put a 160# torque wrench on the axle nuts...
Tapping or Scraping Noise From Rear Wheel Area (Replace Wheel Drive Shaft Nut) #07-04-95-001 - (09/26/2007)
Models: 2004-2008 Chevrolet Corvette and 2004-2008 Cadillac XLR
-------------------------------------------------------------------------------
Condition
Some customers may comment on a tapping or a scraping noise coming from the rear wheel area.
Cause
This condition may be due to the torque on the wheel drive shaft nut relaxing over time.
Correction
Replace the left and the right wheel drive shaft nut following the procedure below.
Remove the center cap from the rim.
Remove and discard the wheel drive shaft nut.
Apply LOCTITE™ 272, or equivalent, to the threads of the axle shaft.
Install the nut and tighten to the new specification.
Tighten
Tighten the nut to 215 N·m (160 lb ft).
Install the center cap to the rim.
Important: The vehicle should not be driven for 24 hours following the repair in order to allow the thread lock to cure.
Parts Information
Part Number.....10257766
Description......Nut
Qty................2 (one per side)
Warranty Information: Labor op F9712 0.3 hr.
Models: 2004-2008 Chevrolet Corvette and 2004-2008 Cadillac XLR
-------------------------------------------------------------------------------
Condition
Some customers may comment on a tapping or a scraping noise coming from the rear wheel area.
Cause
This condition may be due to the torque on the wheel drive shaft nut relaxing over time.
Correction
Replace the left and the right wheel drive shaft nut following the procedure below.
Remove the center cap from the rim.
Remove and discard the wheel drive shaft nut.
Apply LOCTITE™ 272, or equivalent, to the threads of the axle shaft.
Install the nut and tighten to the new specification.
Tighten
Tighten the nut to 215 N·m (160 lb ft).
Install the center cap to the rim.
Important: The vehicle should not be driven for 24 hours following the repair in order to allow the thread lock to cure.
Parts Information
Part Number.....10257766
Description......Nut
Qty................2 (one per side)
Warranty Information: Labor op F9712 0.3 hr.
#15
Le Mans Master
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
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
#16
Drifting
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.
#17
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Location: Cincinnati Ohio
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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.
#19
Drifting
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.
I'm not sure if the rubber is hitting fender liner or muffler, but the noise sounded like something major was broken.