Change rear gear ratio when converting to AOD

[mhjo]

I have ordered a AOD that will replace my C4. I do this because I felt that rpm was too high at 6-70 mph. (I have 3.00 ratio at rear)

Wich rear ratio should I install in connection with the AOD ?

I need balance between good acceleration and relaxing highway driving.

Recommandation?

 

[tx65coupe]

I would say 3.50 gears would be a great setup.

 

[woodsnake]

On a stock motor, a 3.25 or 3.50 are a good choice. I have 3.50's in my 68, but I think I need more rear gear because of my cam's power band.

 

[calpolymustang]

i had a 3.4 with the AOD, and didnt like it. Didnt have as much pep as it i wanted. Since then i've install 4.11s. I like the low gears, but they do make slightly more noise.

By the way, I run at 2350 on the freeway at 70mph, and got 20mpg with an edelbrock 600. Havent rejetted since installing the holley 650

 

[66forfun]

I went 380's and like them very much.

This conversion wasn't cheap and I wanted a good snap for the bucks spent.

Most of the 5.0 foxes were going with 373's for the 5 spds and 411's in the autos.

The highway cruize speeds are ~70mph even if 55 is posted round here and im still under 3200rpm when leading the line of traffic.

 

[rbohm]

with the AOD i suggest using a 3.70 or so rear gear. good off the line dig, and still having a decent highway cruise rpm.

 

[jlangholzj]

with the AOD i suggest using a 3.70 or so rear gear. good off the line dig, and still having a decent highway cruise rpm.

doin the 8.8 sawp for that reason I'm puttin 3.73's in mine. should run around 1850 at 65-70 . kinda pumped

 

[JonK]

My guess would be 3.50/3.55:1 or 3.73:1 depending on what's avail. for your diff., you didn't mention if it's an 8" or 9". Your tire height will be a key in this equation. Here's a handy calculator to get an idea of your RPM's at any speed. I made a spread sheet with my tire ht., AOD overdrive ratio (0.67) and speed to see what my RPM's would change to mainly at 70-80mph and ended up going with 3.50:1 for fun and hwy. Use the calc. to figure out your tire ht. first then plug in the numbers, kinda fun to play with, I checked to see what I'd be turning in 3rd at the drags at 100mph, 110mph, etc. out of curiosity.
Don't forget the taller you go (4.11:1) the shorter your 1st gear on up gets also so it'll shift out of 1st sooner during normal driving with too tall gears.

Randy's Ring & Pinion. RPM Calculator.

Jon

 

[ARPM]

I have ordered a AOD that will replace my C4. I do this because I felt that rpm was too high at 6-70 mph. (I have 3.00 ratio at rear)

Wich rear ratio should I install in connection with the AOD ?

I need balance between good acceleration and relaxing highway driving.

Recommandation?

I had my C4 with 3.55 equalock and 225-45-17" @ rear and was cruising @65mph doing 3,000. The AOD swap lowered to 2,600 and still have an exellent pull in 1/4 mile and a quiet ride.