Rear end noise help please
Thread Starter
Racer
Joined: Mar 2018
Posts: 394
Likes: 51
From: wilmington Ma
Rear end noise help please
81 corvette auto tranny , 55k miles, under acceleration I get a little hum in the rear it goes away when you let off the gas , I had a know good rear end diff installed the noise is still there , also a new leaf spring the car sits higher and the sound is a little louder , is it possible the rear wheel bearing could make noise only under acceleration? I thought for sure it was the diff .
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Your running the correct lube and posi additive in your diff??
you stated, a lttle hum. How noisy is it?
If very slight. Perhaps it's normal? I can't hear it.
you stated, a lttle hum. How noisy is it?
If very slight. Perhaps it's normal? I can't hear it.
Tech Contributor
Joined: Aug 1999
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From: Connecticut, USA
Gear whine about 45-50 mph letting off the gas is usually gear setup, gear cut, or pinion bearings. Depending on the quality of the rebuilt diff and the gears used there may be nothing to do. Either you live with it or you remove it and do it again. If you got any pictures of the pattern and setup spec's that would help. I send fully detailed reports, spec sheets, and pictures of the whole build but I doubt anyone else is so really who knows.
I set up textbook perfect Richmond 355's years ago when they were still made in the USA, they were worst sounding gears I ever heard. It was the gear set, I replaced them with Tom's (US Gear) 355's and set them up the same way, no noise.
A certain amount of gear whine is to be expected with todays gears. Even US Gear printed that in their setup sheet. On top of it you have a DANA diff which I would never put a dime into but still they were quiet when new.
So, is it gear whine from the gear set or bad work?????
I set up textbook perfect Richmond 355's years ago when they were still made in the USA, they were worst sounding gears I ever heard. It was the gear set, I replaced them with Tom's (US Gear) 355's and set them up the same way, no noise.
A certain amount of gear whine is to be expected with todays gears. Even US Gear printed that in their setup sheet. On top of it you have a DANA diff which I would never put a dime into but still they were quiet when new.
So, is it gear whine from the gear set or bad work?????
Is my vette stock?? HAHA
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Wheel bearing noise will change pitch and frequency with acceleration. It usually will start and increase in volume of may accompany a vibration.
If you go to a parking lot and do tight as you can figure 8s, it will tell you.if it's gears, clutch packs, worn bearings.
Also go to the car while it's on the ground and pull on the top of the tire outward, then push so you rock it.....if its a bearing it will clunk.
Jack it up and do the same and you will know if it's the shaft in the diff
If you go to a parking lot and do tight as you can figure 8s, it will tell you.if it's gears, clutch packs, worn bearings.
Also go to the car while it's on the ground and pull on the top of the tire outward, then push so you rock it.....if its a bearing it will clunk.
Jack it up and do the same and you will know if it's the shaft in the diff
Thread Starter
Racer
Joined: Mar 2018
Posts: 394
Likes: 51
From: wilmington Ma
I am having the original diff torn down and inspected , also going to do rear wheel bearings I bought Van Steel loaded bearing supports , I figure 40+ year old bearings and grease are probably not in great condition, I like the car and want it right. Thanks for all the advice.
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If you are thinking the leaf spring changed the driveshaft & pinion angle, No.
Leaf spring is related to the body height. The rear axle stays in the same position.
I would question what lube or I should say, lubes (as in two) were added to the diff.
Leaf spring is related to the body height. The rear axle stays in the same position.
I would question what lube or I should say, lubes (as in two) were added to the diff.
Safety Car
Joined: Nov 2008
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From: Seattle Washington
If you changed the rear diff and the noise is exactly the same, I would eliminate that as the problem. I can certainly believe that You changed one bad one for another bad one, but I would still think the noise would have changed. Is the Gear Ratio stock? Even if you're going to change the Axel Bearings no matter what I would be wiggling the Wheels trying to detect any play before removing the Axels. A worn-out Bushing in the rear of the Trans might possibly be your problem. I assume that putting the Trans in neutral wile slowing down does not fix the noise?
Race Director
Joined: Sep 1999
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From: Plano TX
Here are two things I've discovered about diff whine:
1: Being low on diff fluid makes it louder. I had some whine and figured it couldn't hurt to change the fluid. Some fluid came out the fill hole as I was filling it up and I thought it was full. Went for a drive and the whine was much louder. Turned out I could get another pint into the diff before it was actually full and after that the whine was back to what it was before the fluid change. So always check fluid level.
2: This one is borders on magic and I have no rational explanation for it... I got rid of 99% of my diff noise by changing mufflers. No, I didn't install ridiculously loud mufflers that drown out the whine. The new mufflers are fairly quiet just like the old ones. But the whine all but disappeared. Like I said, I have no rational explanation. In case anyone is curious the old mufflers were Dynomax Ultraflows and the new ones are Magnaflows.
1: Being low on diff fluid makes it louder. I had some whine and figured it couldn't hurt to change the fluid. Some fluid came out the fill hole as I was filling it up and I thought it was full. Went for a drive and the whine was much louder. Turned out I could get another pint into the diff before it was actually full and after that the whine was back to what it was before the fluid change. So always check fluid level.
2: This one is borders on magic and I have no rational explanation for it... I got rid of 99% of my diff noise by changing mufflers. No, I didn't install ridiculously loud mufflers that drown out the whine. The new mufflers are fairly quiet just like the old ones. But the whine all but disappeared. Like I said, I have no rational explanation. In case anyone is curious the old mufflers were Dynomax Ultraflows and the new ones are Magnaflows.
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And I don't run any mufflers and I added sound proofing to the entire rear of my car.
No diff noise.
No diff noise.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
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My exhaust is so loud my car doesn't make any noise
Cruising
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81 corvette auto tranny , 55k miles, under acceleration I get a little hum in the rear it goes away when you let off the gas , I had a know good rear end diff installed the noise is still there , also a new leaf spring the car sits higher and the sound is a little louder , is it possible the rear wheel bearing could make noise only under acceleration? I thought for sure it was the diff .
Tom
Racer
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From: Pikes Peak region Colorado
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This is some funny stuff right there! Reason this made me chuckle is that I took my wife for a ride right after I got the car drivable there were no seals, carpet ,rear interior trim and straight pipes. It was somewhat over or under whelming of a ride. Last weekend I told her that she wouldn't recognize it as being the same vette. It's still kind of loud in a much better way.