Rebuilt differential
Thread Starter
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
Rebuilt differential
Anyone have a source for rebuilt differentials? I was told my '80 may need some serious rear end work and I am investigating my options. Nothing fancy, just a parts replacement is what I'm looking for. Standard factory 3.55 posi setup just like the General built it. Thanks!
Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
Thread Starter
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
As I understand, the General built '80 automatics with 3.55 and 4 speed cars with 3.08 but I have conflicting information. I turn way to many rpm's to have a 3.08. Correct me if I'm wrong, but I'm going by the AIM as it mentions the 3.55. The car turns close to 3K rpm at 60 mph on stock wheels and tires. The window sticker does not mention the rear axle ratio but it is an L48 automatic with Gymkhana and 48 state emissions. How can I tell?
Safety Car
Joined: Nov 2008
Posts: 3,715
Likes: 551
From: Seattle Washington
As I understand, the General built '80 automatics with 3.55 and 4 speed cars with 3.08 but I have conflicting information. I turn way to many rpm's to have a 3.08. Correct me if I'm wrong, but I'm going by the AIM as it mentions the 3.55. The car turns close to 3K rpm at 60 mph on stock wheels and tires. The window sticker does not mention the rear axle ratio but it is an L48 automatic with Gymkhana and 48 state emissions. How can I tell?
1980 3.07 has a OF or OH
1981 2.72 has a OK
1981 2.87 has a OJ or OA
1982 2.72 has a OA or OF
This is from the Corvette by the Numbers book. I will say that there must be something wrong with the 81 82 OA code. The Code should be the same Ratio for both Years.
Pro
Joined: Sep 2011
Posts: 613
Likes: 11
From: EVANSVILLE Wisconsin
As I understand, the General built '80 automatics with 3.55 and 4 speed cars with 3.08 but I have conflicting information. I turn way to many rpm's to have a 3.08. Correct me if I'm wrong, but I'm going by the AIM as it mentions the 3.55. The car turns close to 3K rpm at 60 mph on stock wheels and tires. The window sticker does not mention the rear axle ratio but it is an L48 automatic with Gymkhana and 48 state emissions. How can I tell?
Le Mans Master
Joined: Feb 2011
Posts: 5,943
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From: Southern NH
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Burning Brakes
Joined: Sep 2005
Posts: 895
Likes: 4
From: whitman massachusetts
Diff Rebuild
Not sure if he is still involved with the forum, but do a search for Gary, I think his forum name is/was GTR or GaryGTR. He does real nice work on the earlier c-3 diffs. If you cannot find his info, PM me, I have his number somewhere. Excellent quality work.
Race Director
Joined: May 2003
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From: Science Bitch! Mississauga, Ontario
Canadian Events Coordinator
FWIW, the OP has a 3.07 geared diff. if it's original.
Les
Burning Brakes
Joined: Apr 2011
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From: Phoenix, AZ
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 330
From: Indy Indiana
if you want a standard build with new clutch packs, new bearings, coorrect setup, prepare to pay about 800 at the main vette parts houses. then plan on them milking your core charge for a much as they can to reduce your core charge.
but a standard build will last you 100K miles.
the lower the ratio numerically, the lower your rpms will be at cruising speed..
if you are running 3000 rpm at 60 MPH, you do not have a 3.08, i bet somewhere in the 3.73 4.11 range. which means your rear end has probably been apart in the past.
also factor in a error possibility.. are you really running 60 MPH, are you really running 3000 RPM? torque converter lock up?.. all sorts of factors are in play here.
but a standard build will last you 100K miles.
the lower the ratio numerically, the lower your rpms will be at cruising speed..
if you are running 3000 rpm at 60 MPH, you do not have a 3.08, i bet somewhere in the 3.73 4.11 range. which means your rear end has probably been apart in the past.
also factor in a error possibility.. are you really running 60 MPH, are you really running 3000 RPM? torque converter lock up?.. all sorts of factors are in play here.
Thread Starter
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
I need to get her out and offer a more accurate speedometer/tachometer relationship. To be a little more accurate, the car is turning around 2700rpm at 60 mph. I'm running the stock 350 turbo with lockup and stock size tires. My owners manual shows 3.07 as standard but AIM has 3.55 as optional. The broadcast sheet does not show an optional ratio installed at the factory, so I am genuinely confused. With a 3.07 I would assume something around 2200 or 2300 at 60. I really need to investigate this further on my car...
