Kacey1

So I have a 1982 corvette that Just passed 70 thousand miles. But I’ve been having this noise for alittle bit of time. It’s this vibration/low humming noise coming from my rear end. I also will note that at low gears and at high rpm the noise is non existent but at low gears (especially when accelerating) do I hear that hum/vibration. I’m not sure if the previous owner changes the diff fluid. There is a rear pinion seal leak but it’s not a fast leak. Do you think it could be something with the ring and pinion or maybe the diff fluid?

Big2Bird

Fluid is a good place to start.

HeadsU.P.

That's the thing about the internet. We can't hear a thing. Only you can. You can not describe a noise on the internet. Its impossible.

So, if its not a rear axle fluid issue, it could be one of the six U-Joints. Especially the one near the pinion. Perhaps a needle bearing went south. Perhaps they have seldom been greased.

Sometimes you can grab a driveshaft and just know somethings not right with the U-Joint. Other times there's no clue. Hard to say.

If you change out the fluid, use GM products. If it lasted 40+ yrs, it will last another forty. You will need two Lg bottles of GM lube and one Sm bottle of GM Posi modifier.

7T1vette

Could be U-joints instead of the rear end. But, rear end fluid inspection/change will give you some information. If fluid is replaced and the noise is still there, consider the half-shaft U-joints a a good prospect for that noise.

P.S. Have those U-joints ever been replaced?

Rescue Rogers

u joiints usually dont hum, bearings do. I would suspect a wheel bearing, then maybe a rearend bearing. I would take the drive shaft out and the half shafts and spin the wheels and using a mechanics stethoscope listen to the bearings in each wheel, then do the diff.

av81

Hum only under acceleration ? When you let off gas the noise stops?

7T1vette

Again, you need to check and then change the rear end lube first to know anything about what is going on back there.

Kacey1

So to answer your questions. The u joints have not been changed to my knowledge and will be the next thing I look into. Also the noise does go away after I stop accelerating and is no existent when decelerating. The fluid has not been changed by the pure black color of the fluid which I’m in the process of changing.

blue by you

Make sure when you change the fiuld you add
the posi additive, then go do some slow figure 's
in both directions, good luck

av81

if you're driving down the street foot on gas hearing a hum then let off the gas pedal and the noise stops you have either a bad pinion bearing or worn ring and pinion. My opinion.

Kacey1

I may look into that. Do you know how hard it would be to replace either the bearing or the ring and pinion or both? Should I get a shop to do it?

av81

I would recommend a shop doing the rebuild , or buy a rebuilt diff from Ecklers and do a swap yourself , I think it's around $1150.

Kacey1

Alright. Thanks for the info.

Mark G

If the pinion is leaking I'd definitely start there. Could be the bearing is going and is tearing up the seal. Jack up, put in N and wiggle the driveshaft.

Ideally it would be a good idea if you could put up on jackstands or a hoist, remove the driveshaft, tires and u-joints. Rotate the pinion by hand and feel for roughness. The pinion could still be somewhat tight by wiggling the driveshaft, but sometimes rotating by hand could reveal some bearing 'roughness' which is a tangible sign the bearing is soon to crap out. And when a pinion bearing goes, usually there's little time before lock-up. At that time you can also check the U-joints and even the wheel bearings by doing the wheel bearing test (as in the service manual).

Don't put a floor jack under the pumpkin as they are aluminum and can distort the shape (which who knows ..may have caused your issue to start with).

Kacey1

Ive looked and there is a pinion seal leaking. I’ll definitely check that area tommmarow. Thanks for the helpful info. I really appreciate all of the support

bgall2

My 78 had a noise in the rear end as well. More of a chatter around corners after the car had been drove for a good while. A mechanic suggested that I ALWAYS double the posi track fluid amount and ALWAYS use only GM products. No diff drain on a 78 so I pulled the rear end fluid out.. Put in 2 bottles of GM posi track and filled it up. Has not made a sound since and that was at least 3 years ago.

Kacey1

Alright. Well I’m doing the job today. Fingers crossed. Thanks for the info