C3 differential gear ratio
Thread Starter
Heel & Toe
Joined: Oct 2007
Posts: 23
Likes: 1
C3 differential gear ratio
I was checking to see what gear ratio I have in my '78 L82 4 speed.
Stamped in the bottom flange was 3.12. I have looked in several books and have not even seen 3.12 offered. any ideas. I need to have the diff. rebuilt, what is a good numer to use for better excellaration, won't be doing much hiway driving. I heard 3.55 is good.
thanks
Stamped in the bottom flange was 3.12. I have looked in several books and have not even seen 3.12 offered. any ideas. I need to have the diff. rebuilt, what is a good numer to use for better excellaration, won't be doing much hiway driving. I heard 3.55 is good.
thanks
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
I was checking to see what gear ratio I have in my '78 L82 4 speed.
Stamped in the bottom flange was 3.12. I have looked in several books and have not even seen 3.12 offered. any ideas. I need to have the diff. rebuilt, what is a good numer to use for better excellaration, won't be doing much hiway driving. I heard 3.55 is good.
thanks
Stamped in the bottom flange was 3.12. I have looked in several books and have not even seen 3.12 offered. any ideas. I need to have the diff. rebuilt, what is a good numer to use for better excellaration, won't be doing much hiway driving. I heard 3.55 is good.
thanks
3:73 and a good motor will make it a rocket ship off the line but will limit your freeway speed - though you don't think that will be an issue. I used 4:11 on a car once and was dismayed at the result. I didn't think I'd be doing any freeway driving either but it seemed that with the 4:11 gears I was always uncomfortable over 55 or so. And here in SD you go faster than 55 everywhere!
On that car I wish I had gone to 3:73 - it would have been a lot more streetable.
Pro
Joined: Jun 2009
Posts: 613
Likes: 3
From: Fleetwood PA
Took my 68 bb I recently got out for a quick drive before I started tearing it down for paint. Got 5000 rpm in no time in first.....took a look at the tank sticker......4:11 gears with a close ratio 4 spd.... not a highway cruiser by any means.(hardly a back road cruiser either )The 3:42 or 3:73 would be good with the 3:73 being quicker out of the hole, with the 3:55 in the middle that might be the best choice.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Don't know about 78, but 77's came with a 3.70 behind a manual trasn and 3.55's with an autio. I just put a 3.08 in my 77 and love it. Great on the highway. If I want to get pinned in the seat, I get the 69 out. 454 4 speed and 4:11's. Not real economical to drive, but the grin factor takes over.
