Gear Ratio Change

[Bug8]

I purchased a 3:70 ratio Posi at a local swap meet. Its in great shape and I paid less than $200. How will this work behind a slightly modified 350 with TH400? I have a 383 in the engine stand that will eventally be installed.

 

[bossvette]

Welcome to CAC

do you do a lot of highway driving? I had the same setup (383/auto/3:73) in a street rod and while it was fine in NJ mostly in town driving, when I moved to Ohio and open spaces the gas milage killed me (3000rpm cruise at 55+) 45 mile round trip to work.
I now have the same engine in my Vette with an OD trans and stock gears and 2000 rpm is 70 mph.
If you do a lot of stoplight to stoplight driving and you want to be first to the next light the 3:70 is the way to go.:cool
Craig sr.

 

[Bug8]

I have the stock 3.08 gears now and its a real dog off the line. My car has a high stall speed converter also, so nothing much happens till about 2500 rpm. It is driven on the freeway some, but here in the Seattle area traffic is so bad you rarely get over 60 for any stretch.

 

[bossvette]

I have the stock 3.08 gears now and its a real dog off the line. My car has a high stall speed converter also, so nothing much happens till about 2500 rpm. It is driven on the freeway some, but here in the Seattle area traffic is so bad you rarely get over 60 for any stretch.

in your case the 3:70 would work especially with the 383 and high stall convertor, build your motor for torque and you won't be dissapointed.
The 383 is the best motor Chevy never built.
Craig sr

 

[Stallion]

A big ratio in the rear is the best and easiest modification you can do to get off the line quickest. You won't be dissatisfied with those numbers. It is big enough for good acc., but also not too big (like a whopping 4.11 ) where you will be running high all the time.

 

[Glensgages]

A big ratio in the rear is the best and easiest modification you can do to get off the line quickest....

I swapped the 2.87s in my '82 for 3.73s, and here are my results from strip-testing:
60': were 2.349; now 2.253
330': 6.645 ; 6.337
660': 10.189 @ 70.88 ; 9.751 @ 71.37
1000': 13.289 ; 12.716
1320': 15.903 @ 85.75 ; 15.209 @ 90.69

 

[Stallion]

I swapped the 2.87s in my '82 for 3.73s, and here are my results from strip-testing:
60': were 2.349; now 2.253
330': 6.645 ; 6.337
660': 10.189 @ 70.88 ; 9.751 @ 71.37
1000': 13.289 ; 12.716
1320': 15.903 @ 85.75 ; 15.209 @ 90.69

Wow, drastic changes in numbers with the gear change. Do you need more convincing?

 

[Glensgages]

Had I been able to shove deeper (4.10/4.56) gears in the Dana44 with the stock carrier, I woulda done THAT, too!
I think that 90 MPH was 'just' 4300 RPM in 3rd gear, even WITH a stock Cross-Fire...
4.10s woulda put me at 4700+; 4.56s at just over 5000 RPM