The rear end on my 89 Iroc 5-speed whines only when engaging and disengaging the clutch, and also when I take my foot off the gas it starts to moan. If I am accelerating or giving it constant gas (such as highway crusing) the rear end is quiet, however as soon as i let off the gas it feels like something is loose or out of spec in the back. Any ideas?

Thanks alot!
Matt

 

do you have the right fluids in the rear...

also maybe the pinion nut is loose for some reason. my moms van whines in the rear after replacing the bearing/seal. i guess i didnt tighten that nut down enough.

just a guess though.

 

I have a 91 RS and mine does the same exact thing, I was fixing to change the rear end gear oil but what is the best to use??

 

My 5-speed does the same thing. I changed the rear end oil with Valvoline Synthetic 80w90. It really didn't help much. I check my axle seals and no leaks and the pinion nut wasn't loose either. My automatic has about the same mileage on it and doesn't have that problem. I'm beginning to think that the T-5 may add stresses to those rear ends. I've settled a rebuild and a gear upgrade when the modding begins. Good luck.

 

Your sure its not your clutch right? Check those U joints also. GM sells the proper fluid with additive for those that dont know which fluid to use.