3.90 diiferentials imploding?
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Instructor
Joined: Aug 1999
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From: Chandler AZ
3.90 diiferentials imploding?
I've been thinking about getting a 3.90 rear differential for my 99 M6 coupe. Someone just told me that the 3.90 is not recommended as this requires the case to be ground, which causes it to weaken and may lead to failure. HAs anyone heard of someones differential imploding after a gear change?
Instructor
Joined: Dec 2002
Posts: 155
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From: Bristol Tenn.
Re: 3.90 diiferentials imploding? (ElanMike)
If you have a 3.15 or 3.42 gear in your car now nothing has to be done to the case to accept the higher gear ratios. If you buy the complete diff. assembly with the 3.90 gears already installed the case has not been weakend any. I have never heard of turning a case down, the tolerances are very tight on the diff. assemblys and I would not recommend this. Buy the complete getrag unit or put the gears in your existing case if they will fit. I have a 3.15 case that I had 3.90's in and have just installed 3.73's. Hope this helps. Nate
Race Director
Joined: Mar 2000
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From: Palm City Florida
Re: 3.90 diiferentials imploding? (ElanMike)
I've been thinking about getting a 3.90 rear differential for my 99 M6 coupe. Someone just told me that the 3.90 is not recommended as this requires the case to be ground, which causes it to weaken and may lead to failure. HAs anyone heard of someones differential imploding after a gear change?
Some idiot sent me an e-mail one time responding to my post about installing 4.10's. He told me they have to "HOG" out the differential case and it weakens the structure...I just laughed...Nothing like misinformation being passed around like fact... :rolleyes:
Do the gears and be happy...No worries... :cool:
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From: Central Jersey
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Re: 3.90 diiferentials imploding? (chuckster)
You dont have to modify the case in anyway. We have built many sets of 3.90's :) :)
Racer
Joined: Jan 2003
Posts: 493
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From: Goose Creek SC
Re: 3.90 diiferentials imploding? (ElanMike)
I have never heard of this either. I have heard that hardened output shafts are recommended on manual transmission equipped cars with 3.90 or numerically higher gears.
Is there any truth to that?
Is there any truth to that?
Melting Slicks
Joined: Oct 2002
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Re: 3.90 diiferentials imploding? (knowledgefreak)
It's my understanding that they make the ring gear a little narrower to fit the cast but the case is never touched thats why they generally only accept 3.42 gears in exchange as the case is superior to some of the higher ratios.
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Race Director
Joined: Mar 2000
Posts: 17,602
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From: Palm City Florida
Re: 3.90 diiferentials imploding? (knowledgefreak)
I don't think there is a single case (Pun Intended) of a case grenading becuase of the higher gear ratio..there are tons who have snapped shafts..So that tells me that is the weakest link today....
Lot's of 4.10's out there and happy...
;)
Lot's of 4.10's out there and happy...
;)
