ChevyMan1989

So im to the point in my build where im building the rear. i picked up a 12 bolt out of a 68 chevelle with an open diff and 3.08 gears. I have no clue what gear ratio i should run. The car is a 70 chevelle with an LQ4 and a T56. I swapped to an ls1 intake long tube headers pretty much stock rebuild with a pretty healthy cam and im going to be putting a locker in the rear. there are a lot of mountains and hills where i live and i will rarely but sometimes be on highways and occasionally take it to the track. im looking more for the bottom end torque then top end. does anyone have any suggestions/advice on a good gear ratio for me?

99VetteFRC

I have 4.10s in my Chevelle. Loved them with the OD trans... Hate them without. I hear boosted should have less gear though. I may put the 3.08s back in after the turbos are on. Trial and error I guess.

oldgoat69

I have 3.50 with a 4L60E, 2300 rpm at 70mph, 26" tall tires. Very pleasant to drive overall.

c6matt

iTrader: (1)

dont even think of going less than a 3.73 with a t56. I swapped from 3.08's to 3.73 when i did the t56 swap and always wished i did 4.11's. That .5 OD is amazing. 4.11's and dont look back. if you had boost i would say 3.73s just because 1st would be useless..

2165 Turbo Rail

iTrader: (1)

the GTO has 3.50 and I think that's perfect for a boosted car, but like the rest said, go closer to 3.73 - 4.10 with a t56

bczee

iTrader: (12)

I have 4.10 with a Viper T56.. 275x40x17 tires. @ 65mph I am doing 1750rpm.. but I usually curise around 2000-2200 rpm and still get 26 mpg on the Highway.

BC

99VetteFRC

Like my Vette!!!

gMAG

iTrader: (1)

I like the 3.70s with 27 inch tires.
Having it to do over again, I'd opt for just a bit more...maybe 3.90 or so.
See sig.

BrianSF-GA

If you know your trap speed or an estimate, trap in 4th gear (1:1) at or near your rev limiter or where your motor starts dropping horspower, but, you will have to decide what rear tire O.D. you are going to run first. Your overdrive gears (5th & 6th) will help with your streetability.

... use this calculator http://www.f-body.org/gears/

ChevyMan1989

thanks guys. you def helped me make a decision. 4.10s it is!