97-04 Chevrolet Corvette 700 - 900 RPM Buzz, Moan, Rattle, Resonance Noise on Acceleration - kw 5.7 LS1 LS6 Z06 absorber accelerate axle bracket damper differential exhaust insulator launch mount turn

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Customer may complain of a rattle or resonance type noise from the rear of the vehicle. The concern will be most noticeable under acceleration around 700 - 900 RPMs. The concern may be perceived as exhaust related or an internal concern with the rear differential.

As with any customer concern that is of a subjective nature (i.e. exhaust tone), a vehicle comparison is a recommended first step. Also note that the 01 ZO6 Corvette has a specially tuned exhaust to give it a more aggressive sound. The 02 ZO6 has been further tuned to be even more aggressive than the 01. If the noise is deemed abnormal, there are 4 possible areas to be investigated:

1. "Hard" contact between the transmission mount studs and the aluminum crossmember cradle could cause unwanted vehicle resonance. If hard contact condition is found, either of the following may help:

a. Loosen the mount and "rebed" the transmission.

b. Slotting the holes front to back in the crossmember and allowing the mount to reposition rearward.

2. Modifications or variances in driveline working angles may contribute to unwanted resonance.

a. Modifications - If the customer has lowered the vehicle the driveline working angles have also changed. Set the vehicle ride height at the high end of the specification (especially the rear) using service information.

b. Variance - If a build variance is contributing to the concern, a 1/4 inch shim can be added between the rubber mount and aluminum cross member cradle. This will actually raise the rear axle.

3. Actual exhaust or rear differential concern (after above have been tried / evaluated):

* Review 00-06-05-002 (2000 YB) "Exhaust boom at 1500 rpm" (install spacers to exhaust hangers).

* Review 83-66-07 (97 - 98) "Exhaust muffler insulator rumble noise" (replace mufflers).

4. Manipulation of the damper / tuned absorber located on the rear axle differential may improve the concern. Perform the following:

a. Remove the damper and evaluate concern.

b. Install damper from another vehicle (or service parts if in stock) and evaluate.

During the 2000 model year, a damper change was implemented in production but there was no part number change. Installing a 2001 damper on a 2000 or older model year vehicle should have the most positive impact on the concern. However, a variation +/- 15% in dampers of the same model year does exist so trying multiple dampers of the same vintage may help.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

(97 Chevrolet Corvette) and (98 Chevrolet Corvette) and (99 Chevrolet Corvette) and (00 Chevrolet Corvette) and (01 Chevrolet Corvette) and (02 Chevrolet Corvette) and (03 Chevrolet Corvette) and (04 Chevrolet Corvette)

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