New differential whine
Thread Starter
Le Mans Master
Joined: Apr 2006
Posts: 5,933
Likes: 13
From: The Beautiful Inland Empire WA.
New differential whine
I had a brand new 3.73 differential installed in my 98 Corvette A4 about a month ago. The first thing the mechanic did after taking it down off of the rack was to lay about 35 feet of dark black rubber in their parking lot --- to make sure that everything worked........
OK, guess what? completely predictably, the diff whined like crazy for the first couple of 100 miles then began to get quieter. I now have about 1000 miles on it and it is probably 20% as loud as it was at first. I did replace the lube after 600 miles.
The whine is still noticeable if I have the windows up and the radio off, but otherwise not too bad. If I am listening to the radio at even moderate volume, I do not hear it all. It does not whine at all at cruising speeds, only on moderate acceleration and decelleration.
My question is this --- I KNOW that once they start to whine they will always whine. BUT what about 10,000 miles from now or longer? Do they get noisier? The mechanic admitted that he did not read the warnings that came with the diff to take it easy for 350 miles (which I did for the rest of the time....). I really like the shop I took it to, and would hate to stick them with a $2,000 repair bill if it is not going to get any worse than it is right now............opinions please?
OK, guess what? completely predictably, the diff whined like crazy for the first couple of 100 miles then began to get quieter. I now have about 1000 miles on it and it is probably 20% as loud as it was at first. I did replace the lube after 600 miles.
The whine is still noticeable if I have the windows up and the radio off, but otherwise not too bad. If I am listening to the radio at even moderate volume, I do not hear it all. It does not whine at all at cruising speeds, only on moderate acceleration and decelleration.
My question is this --- I KNOW that once they start to whine they will always whine. BUT what about 10,000 miles from now or longer? Do they get noisier? The mechanic admitted that he did not read the warnings that came with the diff to take it easy for 350 miles (which I did for the rest of the time....). I really like the shop I took it to, and would hate to stick them with a $2,000 repair bill if it is not going to get any worse than it is right now............opinions please?
Last edited by C6NRED; Jun 4, 2007 at 05:35 PM.
Racer
Joined: Feb 2007
Posts: 296
Likes: 0
From: Landisville PA
Although you like the shop you took it to, the 'mechanic' should know better than to treat new gears like he did. He should know better, and not need to read any warnings. It's common sense.
We haven't done any Corvette gear swapping, but have had our Wrangler gears done. You've got to take it easy on the gears until they're broken in.
I also understand that the gear whine is due to the pinion being set deep in the ring gear. This doesn't mean the gears are set up wrong, just tight. This may be perfect for a track car, but not ideal for a street driven car.
Also, is the rear cover "HOT" to touch after a short drive?
We haven't done any Corvette gear swapping, but have had our Wrangler gears done. You've got to take it easy on the gears until they're broken in.
I also understand that the gear whine is due to the pinion being set deep in the ring gear. This doesn't mean the gears are set up wrong, just tight. This may be perfect for a track car, but not ideal for a street driven car.
Also, is the rear cover "HOT" to touch after a short drive?
Burning Brakes
Joined: Jul 2006
Posts: 875
Likes: 1
w/ any customer cars..let alone..violating the warnings
that came w/ the part.
Be thankful that mechanic wasn't your doctor...people get
damaged from prescriptions because guess
what the doctors didn't bother to read the warning labels.
Thread Starter
Le Mans Master
Joined: Apr 2006
Posts: 5,933
Likes: 13
From: The Beautiful Inland Empire WA.
Also, is the rear cover "HOT" to the touch....
The trans runs at around 200 to 205 and the rear gears and exhaust are all back there in close proximity...I wouldn't know what "hot" feels like to my bare hand on this car.......
To all.....when I say that I really like the mechanic, I don't mean to say that I am being soft hearted here....I am thinking about making him put HUD in my car for free and calling it even...providing I can put up with the noise from the rear end.........
The trans runs at around 200 to 205 and the rear gears and exhaust are all back there in close proximity...I wouldn't know what "hot" feels like to my bare hand on this car.......
To all.....when I say that I really like the mechanic, I don't mean to say that I am being soft hearted here....I am thinking about making him put HUD in my car for free and calling it even...providing I can put up with the noise from the rear end.........
Last edited by C6NRED; Jun 4, 2007 at 05:34 PM.
Burning Brakes
Joined: Dec 2006
Posts: 1,092
Likes: 0
From: Deerfield VA
St. Jude Donor '07
A mechanic with common sense, and a lot of experience would never do what you described. New parts must seat and burnish smoothly. In effect, what he could have done is scratch, mar, or gall the gear teeth contact areas, or bearings. I can't say unequivocally that is your problem, but metallurgy is metallurgy, and a rear that is set up properly, and carefully broken in should be SILENT.
John
John
Le Mans Master
Joined: Jan 2003
Posts: 6,059
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From: AKA Harvey Mushman-I know just enough to be dangerous "Those who sacrifice liberty for safety deserve neither"- B. Franklin
Senior Member
Cruise-In V Veteran
He owes you the HUD install for the 35 feet of rubber. Just don't let him show off to you with your own car again. Sorry for the off subject, hopefully the next poster can answer your question.
Edit- looks like B&T already answered while I was typing.
Edit- looks like B&T already answered while I was typing.
Burning Brakes
Joined: Dec 2006
Posts: 1,092
Likes: 0
From: Deerfield VA
St. Jude Donor '07
There are two critical things required in setting a rear for quiet operation, centering the pinion depth, basically centering it in the ring gear so the load is borne direct center of the pinion gear, second, the depth of tooth into the mating gear tooth. If done properly, the tooth contact patch (shown by painting the tooth with white lead) will be perfectly centered between the tooth tip and root. If this is done properly, the backlash, the amount of clearance between the teeth when rocked back and forth would be about .007, and the rear should be quiet if machined properly.
When I was kid everyone was afraid of setting gears, my dad owned a tool and die business, so he explained the procedure in the service manual to me, and how to precisely measure the clearances. I spent a lot of time learning his trade, it sure helped when I rebuilt trannies, rears, and engines. PRECISION IS EVERYTHING. And from the new GM techs I've trained, if the micrometers aren't digital, They are LOST, good young mechanics are hard to find, precision measuring is an art to itself!
John
When I was kid everyone was afraid of setting gears, my dad owned a tool and die business, so he explained the procedure in the service manual to me, and how to precisely measure the clearances. I spent a lot of time learning his trade, it sure helped when I rebuilt trannies, rears, and engines. PRECISION IS EVERYTHING. And from the new GM techs I've trained, if the micrometers aren't digital, They are LOST, good young mechanics are hard to find, precision measuring is an art to itself!
John
Last edited by Black 'n Tan; Jun 4, 2007 at 05:54 PM.
Race Director
Joined: Nov 2001
Posts: 18,682
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St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12
Your mechanic screwed up big time. I would say make him pay for the replacement. It will only get worst as the time passes.
When I installed my DTE 3.90s I made sure to break them in per instructions and even over killed it by taking it easy for upto 1000 miles. Changed the oil and my differential is quiet as OEM. I have 3000 miles on it now and no whine.
When I installed my DTE 3.90s I made sure to break them in per instructions and even over killed it by taking it easy for upto 1000 miles. Changed the oil and my differential is quiet as OEM. I have 3000 miles on it now and no whine.
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Burning Brakes
Joined: Nov 2006
Posts: 961
Likes: 0
From: Torrance CA
I definitely think that the mechanic should pay for it. he should know that gears need to be broken in before WOT.
When I got my gears I broke mine in for 300 miles, it was really hard to do but I got through it and I have absolutely no whine.
When I got my gears I broke mine in for 300 miles, it was really hard to do but I got through it and I have absolutely no whine.
