I have a 1988, 3.27, 9-bolt, IROC. I purchased the car a few months ago and it came with the noise. Noise is a roar that starts with roll off, I feel no roughness or slop when I drive the car. The noise seems to come equaly from all areas of the rear end. I emailed the guy that sold me the car and he said the noise started "about" the time he put tires on it. Tire pressure and road surface do not seem to change the pitch or amilitude of the roar and I do not hear the sound from the front tires (same tires and milage).

Might I have a bad bearing? Ring and pinion? Both? I plan to pull the cover and axels this weekend and look around some. I have read here that if the wear pattern is consistent and no cracks/fractures then the gears are ok.

What else do I look for before I start throwing money at it?

Any info is greatly appreciated.

 

Are the tires directional? Might want to make sure they were put on the right way.

 

Thanks for the suggestion, I checked the tires and all is ok there.

 

Pull the cover. A bad bearing in the rear will fill the lube with a metalflake looking stuff, real easy to see at the bottom of the case or on the magnet. A pinion bearing might let the pinion shaft move back and forth a bit with no tension on the driveshaft. Usually a bad pinion bearing will make a racket when you let off the gas. A bad carrier bearing will start with a pulsing grinding or roaring sound sometimes, hard to figure whether it's an axle bearing or on the carrier.

 

That is my plan for the weekend. Pull the cover and the driver side axel as the noise seems to come more from there. Noise is roar only, no pulsing, clank or anything else...roar seems to change pitch with speed and become less pronounced as speed increases and then at 70 a slight vibration starts.