Manual vs. Auto Diff
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From: Hudson WI
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Manual vs. Auto Diff
I want to build a new diff for my car. I know I don't want 05 diff, but I find several newer diffs from auto trans cars. Is the gear ratio the only difference?
The plan is 3.73 gears, so the stack gears don't matter. Basically need it as a core.
Thanks!
The plan is 3.73 gears, so the stack gears don't matter. Basically need it as a core.
Thanks!
Race Director
Joined: Mar 2005
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From: Austin Texas
It may have changed but the '05 auto 2.73 diff case was smaller than the manual case. 3.42 gears from the manual were too large to fit the 2.73 automatic case.
Some companies were making ring and pinion sets in other ratios for either case and for later model C6's though.
Some companies were making ring and pinion sets in other ratios for either case and for later model C6's though.
Thread Starter
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From: Hudson WI
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It may have changed but the '05 auto 2.73 diff case was smaller than the manual case. 3.42 gears from the manual were too large to fit the 2.73 automatic case.
Some companies were making ring and pinion sets in other ratios for either case and for later model C6's though.
Some companies were making ring and pinion sets in other ratios for either case and for later model C6's though.
Race Director
Joined: Mar 2005
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From: Austin Texas
Ratio depends on tooth count of ring gear and pinion gear, More teeth requires a larger ring and pinion to keep the same minimum tooth size.
The higher ratio of 3.73 requires more teeth than a 2.56/2,73, more teeth rquires a larger ring and pinion.
Logic would lead me to think a higher numeric ratio would require a larger ring and pinion. Larger ring and pinion means a larger diff case? Maybe why the 9" Ford is popular and stronger than the 8.8" Ford?
The higher ratio of 3.73 requires more teeth than a 2.56/2,73, more teeth rquires a larger ring and pinion.
Logic would lead me to think a higher numeric ratio would require a larger ring and pinion. Larger ring and pinion means a larger diff case? Maybe why the 9" Ford is popular and stronger than the 8.8" Ford?
Safety Car
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From: Oshawa, Ontario
You can use the 06 manual differential in your 05 auto. 06 manual diff comes with 3.42 gear and 3.73 gear will work with it. dont think auto 06 diff will work with 3.73 gear but may be mistaken on that. need diff that works with 27 spline output shaft of your 05 auto.first couple years of A6 diff's compatible with 27 spline A4's. possibly the 3.15 geared auto 06 diff may be able to run the 3.73 gear
Last edited by irok; Sep 16, 2012 at 10:56 AM.
Thread Starter
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From: Hudson WI
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You can use the 06 manual differential in your 05 auto. 06 manual diff comes with 3.42 gear and 3.73 gear will work with it. dont think auto 06 diff will work with 3.73 gear but may be mistaken on that. need diff that works with 27 spline output shaft of your 05 auto.first couple years of A6 compatible with 27 spline A4's. possibly the 3.15 geared auto 06 diff may be able to run the 3.73 gear
Now I know why auto diffs are so much cheaper.
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From: Austin Texas
You can use the 06 manual differential in your 05 auto. 06 manual diff comes with 3.42 gear and 3.73 gear will work with it. dont think auto 06 diff will work with 3.73 gear but may be mistaken on that. need diff that works with 27 spline output shaft of your 05 auto.first couple years of A6 compatible with 27 spline A4's. possibly the 3.15 geared auto 06 diff may be able to run the 3.73 gear
Team Owner
Joined: Feb 2001
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From: Short Hills, NJ
If ya can, try and go with the newest/latest model year rear that you can find as there were some minor updates/upgrades (added ribbing, thicker areas etc.) even from the 'already improved' 2006 version to the present.
2006 and 2007 automatic rears were 2.56 only and 2008 and up automatic rears came in both 2.56 and 2.73 depending on model/options.
During the C6 era, only the 2005 automatics (with their weaker rear) had an available/optional 3.15 ratio.
2006 and 2007 automatic rears were 2.56 only and 2008 and up automatic rears came in both 2.56 and 2.73 depending on model/options. During the C6 era, only the 2005 automatics (with their weaker rear) had an available/optional 3.15 ratio.
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Thread Starter
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From: Hudson WI
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So I should be able to by the case and ends for less than that. I want to use the new Eaton carrier with the extra bearing and hardened output shafts.
Thanks!
UPDATE GMPARTSHOUSE wants almost $3K for diff based on what their website says.
Thanks!
UPDATE GMPARTSHOUSE wants almost $3K for diff based on what their website says.
Last edited by timd38; Sep 16, 2012 at 06:56 PM.
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You must have just looked at the carrier, the new diff is much more expensive than that.
The automatic 06 will actually work but it will need some small machine work done on it. If you can get it cheap, then get one. The gear is not a big deal, while it will have a 2 series carrier, you can get a thick ring gear which will solve that. The only issue is the housing for the manual and automatic is the same, but the VSS on the auto is not final machined. The speed is picked up in the tranny on an automatic car. We machine them all the time, I seem to end up with automatic cores all the time, so we fly cut and drill the casting. The vss boss is already in the case, the casting is the same between auto and standard. A machine shop should be able to do this for easily. Like I said, if you can find it cheap then get it.
The automatic 06 will actually work but it will need some small machine work done on it. If you can get it cheap, then get one. The gear is not a big deal, while it will have a 2 series carrier, you can get a thick ring gear which will solve that. The only issue is the housing for the manual and automatic is the same, but the VSS on the auto is not final machined. The speed is picked up in the tranny on an automatic car. We machine them all the time, I seem to end up with automatic cores all the time, so we fly cut and drill the casting. The vss boss is already in the case, the casting is the same between auto and standard. A machine shop should be able to do this for easily. Like I said, if you can find it cheap then get it.
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From: Oshawa, Ontario
If your lucky sometimes it pays to shop around. I bought a new 08 ZO6 3.42 diff for $1,450. that we installed in an 09 A6 Z51 car. guess I should have bought all he had. I see the 2nd design manual case and covers available for $ 671. without axle cooling. the Z06 diff I bought does retail for $3,300. at dealer
Last edited by irok; Sep 17, 2012 at 12:32 PM.
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If your lucky sometimes it pays to shop around. I bought a new 08 ZO6 3.42 diff for $1,450. that we installed in an 09 A6 Z51 car. guess I should have bought all he had. I see the 2nd design manual case and covers available for $ 671. without axle cooling. the Z06 diff I bought does retail for $3,300. at dealer
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From: Short Hills, NJ
Thread Starter
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
Team Owner
Joined: Feb 2001
Posts: 27,231
Likes: 117
From: Short Hills, NJ
