Rear end ratio

[fc3]

Hey guys, If I change from 3.08 to say 3.55 or 3.73 how many rpm's will I be turning at 70 mph if the 3.08 is turning 2700 now? At 55 mph it turns 2200 now. Any guesses? Fred.

 

[MoeJr]

With the 3.55's you will be turning close to 3100 RPM.

 

[mvftw]

I have 3.70's and it's fun around town, but it screams on the HiWay. About 3400 @ 65. I would go down to 3.36 but it's All original so I just make sure I have a full tank of gas:cool

 

[fc3]

I failed to mention I have a 400 Turbo tranny, 235-60, 15" tires. Fred.

 

[69MyWay]

I am running 3.55 rear gears and run right at 3,000 or 3,100 or so at 70 mph. I get 12 mpg cruising that way with the big block engine just humming along. You gotta love EFI.

 

[GaryS]

Go to the following website and plug in your variables. As a note, I use 26" for the tire diameter.

http://www.idavette.net/tech/ratioc.htm

Gary

 

[crebo]

This won't help much but I'll say it anyway.
I'm turning 2500 at 85 mph with a big block. I have a 700r4 thru BowTie overdrives.
I want to go to 3:55 or 3:70...
Chris can you rip it up pretty good with the 3:55's?

 

[fc3]

Gary, The calculator is great!!! Thanks. Chris- the 6 speed doesn't hurt either.Fred :cool

 

[Tom Bryant]

Hey guys!! Look up at the top of this page. Click on the Tools tab. You might be suprised at what you find.

Tom

 

[69MyWay]

This won't help much but I'll say it anyway.
I'm turning 2500 at 85 mph with a big block. I have a 700r4 thru BowTie overdrives.
I want to go to 3:55 or 3:70...
Chris can you rip it up pretty good with the 3:55's?

Yep, she pulls prett hard in about any gear with this combo. IN a perfect world I would have 3.73 rear gears and an overdrive stick shift trans.