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I replaced my differential with a rebuilt unit. There is a whine coming from the diff. when the car is coasting in gear but goes away with the drive train is under a load. Noise seems worse than the unit I took out which was leaking at all three yoke seals. Is this normal or could there be a setup problem with the rebuilt unit? Thanks in advance for your advice.
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Where did you purchase it from?
Did you follow the break in procedure?
Do they warranty it?
After much research, I had mine done by Precision Corvette Differential in Garland TX.
The owner Mike Dyer did an exceptional job rebuilding and beefing up the weak aluminum Dana 44 in the '81. It is quite and leak free.
I hope you didn't buy yours from Duntov Motors.
GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975
Click here to see more pics of my Vette on CarDomain.
Lifetime Member #26
Borgeson Steering Box
Born 8/1981
Sequence #3975
Click here to see more pics of my Vette on CarDomain.
Lifetime Member #26
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
ANY noise from the dif is ABnormal...the only time a noise would be considered "normal" would be with the low ratio(4.11, 4.88, etc).
Take it back....it will only get worse, and yes, it is an assembly error....or they put used gears in...
Joel Adams
C3VR Lifetime Member #56 
My Link 
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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Joel, will using an insufficient amount, or none at all, of the posi additive cause a noise? I seem to remember having noise once and adding a second bottle of GM fluid and that caused the noise to go away. But I don't think it was gear whine, it was a squeak or something like that.
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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I'll tell you right now with no if ands or buts, that rear is not right. It most likely does not have enough pinion depth. Corvette rears are quiet and very rarely have any noise at all
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
daveo76 said: Joel, will using an insufficient amount, or none at all, of the posi additive cause a noise? I seem to remember having noise once and adding a second bottle of GM fluid and that caused the noise to go away. But I don't think it was gear whine, it was a squeak or something like that.
The posi additive is ONLY used to condition the clutches in the diff...it has absolutely NO bearing(no pun intended) on whether or not the gears howl when either accelerating, or decelerating....that noise is due to the gears not being properly set up....period.
My suggestion is to take it back to whomever did the work, if possible. The more you drive it the worse it's gunna get. If you don't have many miles on them(less than 50 or so), they MIGHT be able to fix it. If they have more miles than that....it's doubtful they will ever be right, even if they gears do get set correctly. Once the gears get run in....they're in. 
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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I contacted the folks that sold me the unit and they told me to send it back. Hopefully the second time will be a winner.
Thanks for the advice.
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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in Forum: C3 Engines, Driveline and Handling
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