I'm in the process of restoring a 1991 Camaro Z28 (350 TPI).
I just had the original rear end gears replaced with new 3.42 gears. Now there is a horrible noise at around 40 mph. No noise below 40 mph and no noise above around 44 mph. I had my mechanic check it twice and he couldn't find anything wrong? Could he be missing something or is he hiding something from me. He also told me that this car has a floating axle and that he did everything correctly. My mechanic is a certified mechanic and comes highly recomended. I'm at a loss. Any suggestions?

 

does it make like a howling noise? and does it sound like it's coming from the rear? Did he replace the bearings too? You can over torque the pinion nut and crush the crush sleeve to much when installing new gears making no backlash or not enough backlash. When installing gears they must be prefect otherwise everything gets f***ed. I'd test drive the car with him in it and make sure you pin point the noise you hear. It's been a while since i put gears in maybe 2 years or so everyone would laugh at me because i'd take my damn time, but when people rush installing gears they really can f** up and have to replace and reinstall everything all over again. If it is your rear GM has a additive you can add to the fuild that might help but the Tech should be the one to put that in. good luck

 

Yes, all bearings were replaced. This was a complete rebuild. The noise is definitely coming from the rear end.

 

Did you use a new gearset or a used gearset?

The reason I ask is that the setup procedure is different. With new gears you primarily pay attention to th drive side paterna dn the backlash. With used gears you primarily pay attention to the coast side. I'm wary of used gears as a general rule anyway.

If the gears were set up incorrectly you'd get howling nearly all the time. Some gearsets are just noisey, like Richmonds. You can install them correctly, and they still howl a little; it's just how they are made. I have started usign Yukon gears exclusively because they are just as stong, but make no noise. They also set up well, usually with factory or very near factory shims, which saves time.