I have an 82 and the rearend has the batwing. I hear a low level whining noise at low speeds. I am not sure if it is tire noise or a rearend whine. I want to go ahead and change the fluid in the rearend. What is the best method for removing the old fluid? What fluid and additives do I need to go back with. Is there an easy way to open the rearend to inspect for damage or missing teeth? Any tips or help would be greatly appreciated.

 

I'm kind of new to 'Vettes, but I've done a lot of reading over the long cold winter. My 'Vette has a small amount of noise coming from the rear end as well, so I've tried to absorb as much as I can on the subject.

From "How To Restore and Modify Your Corvette 1968-82" I read that the only common problem with the Corvette Positraction rear end is that the Positraction additave has worn out. This is noticed as a noise when going round a corner at slow speed. Changing the fluid can prevent the problem. Use a gear oil designed for Positraction. You can apparently also buy Positraction additive, but I've never seen it. Changing the fluid should be fairly straight forward. Pull the lower plug to drain, replace it and pull the upper plug and fill until it runs out. This is a job that's on my list for this spring.

Second thing to check, this one from my own limited experience, is the universal joints between the differential and the wheel berrings. On my car they are a little tight and make a small amount of noise. When I replace them I'll pay the extra dollar and get the ones with the grease zirk. Same for the drive shaft.

Last, are you sure it isn't a rear wheel berring? Everything is connected and the sound can travel up to the solid frame mount for the differential. I drove one car in my search for the right C3 that had a very bad wheel berring, and the noise seemed to come from both the side and the center.

As for inspection - the rear cover can be pulled, but the rear leaf spring mounts to the cover so it is a bit of a job. I haven't done this (yet) so I can't comment on how long it may take.

All the best,
- Paul

 

Paul, If you have an upper and lower plug your lucky. I only see one plug on mine and I think I have to syphon out the old and then fill to the plug level with new. I just wanted to confirm this. What year is your Vette?

 

all right guys help me out here. I am a novice mechanic at best. Everything I do is what I teach myself after reading or getting pointers from you guys. The rest is trail and error. I just dont want my trial and error to take all weekend and end up at a real mechanic's shop with a bill for a rearend replacement.

 

I went to Advanced Auto and bought a hand pump it looks like a large syringe only metal with a clear plastic tube. I sucked all my fluid out and replaced it with GM fluid and additive. No big deal took about 45 mins.

 

There is only a fill plug on my 69, no drain plug. I'd like to discuss that with a GM engineer someday. Siphon is the only way out unless you're taking apart the rear end.
If I ever have to have mine rebuilt, GTR1999 here in the forum puts in a drain plug.
I guess GM figured that the fluid they put in at the plant was good for the life of the car, eh?

 

Kent. Does the whining noise change tone, get stronger or go away depending on if accelerating, running at a steady speed, or coasting? Mine has a slight whining noise when running down the road at a steady speed, but goes away when I let up on the throttle. If this is the type of noise you are hearing, it is the probably the ring-and-pinion in the the rear-end, but I don’t think it is anything to worry about. Mine has been whining for 20 years and 150k miles, nor has the tone changed.
-Jim

 

Well, I bought my 'Vette last November, just before the snow. Today I jacked up the front for the first time. I still have not jacked up the back, so I'll have to defer to the experts. The two plug comment was based on experience with other differentials, not the 'Vette. I assumed... Bad idea I guess.

Feeling silly now,

- Paul

 

It seems to be a constant whine at cruising speed. It is not a loud whine but it is definately there. I dont hear it under full throttle or heavy accelaeration. I do hear though whil constant on the throttle and at coasting. Paul dont feel silly. There are a lot of "why in the heck did GM do this or not do this with Vettes" You would think anything containing fluid would have a fill and drain plug including the rearend housing and transmission pan.

 

I just syphoned out with that big syringe, it was very muddy and hard to suck it out. put some newspapers on the pavement, I really did a big mess!

I put 1 1/2 qts of Lucas posi gear lube

 

My '82 had a noticable whine that was due to wear caused by running the rear end low on lube (Bubba, teh previous owner). A side yoke seal was leaking and throwing oil all over the bottom of the car. I pulled the rear end and had Van Steele rebuild it. I reinstalled it and used GM posi lube and GM posi additive. The rear end is much quieter but if you listen hard, you can still hear a slight whine. I think it is because you are basically sitting right near the rear end and can't avoid hearing even the slightest noise. (You could get louder mufflers or turn the radio up a bit!)

 

My car is loud when running At idle it vibrates the windows in my daughters room right above the garage. I cant start the car after they go to bed. As far as the stereo goes I havr 2 350watt Kenwwod 6x9 speakers powered by a bridged 800 watt kenwood amp! I cant hear anything else but music when its cranked up!

 

Well I changed the rear diff oil last night. It was easy. I sucked all of the old out with the metal canister syringe. The oil was black as night.
I went back wit 80-90w Lucas and put the additive in well just because even though the Lucas bottle stated it was not needed. The hardest part of the project was removing the plug. The whole process only took about 30 min. I have had the spare tire carrier removed from the car for about a year now. The extra room under the rear is nice when working on theat area of the car. I think I am going to tackle half-shaft U joints brakes and bearings next.