What gears should i run behind 3 speed trans??

[BoBax]

I have a 383 motor with the original 3 speed automatic. When riding down the road the motor is turning some heavy RPM's. I was thinking of changing the rear end out maybe going to some 355's . I know I will lose some bottom end but that's not a problem cause im wanting it to cruise. ANY SUGESTIONS??????

 

[69hemibeep]

Any Idea what is in there and how fast do you need to cruise? Lots of runners came with 323's. Try this http://www.wallaceracing.com/calc-rpm.php

 

[quikbird]

If you want to lower the rpm at cruise then the rear end gears will need to go lower. Usually a 323 or276 ratio.
Another option is gear vender overdrive. Can have grunt and cruise with it.

 

[Basketcase]

3.23s are great all around gears. I had 3.55s behind a 440 4 speed, and it loved 70 on the highway, great take off.

 

[Coyote]

A lot of MOPARS (including cop cars) came with a 3.23 open. Cop cars would run 135-140 mph with the healthy engines. It's a decent real world gear ratio. I have 3:55 in my 440 4 gear powered Satellite and have done a Drag Week with it. It's not a killer gear, but I would not want to go much steeper and still use it on the road. It would get real busy under hood. I'm running a 3:54 Dana 60 in my '55 Brand "C" with a Tremec 5 gear overdrive. It works great at 80+ on the road.

 

[Danomt]

I am with the 3.23 crowd. Good all around gear...

 

[Ranger]

Same here. Got a 3.23 in mine and I turn 2800 @ 70 MPH (2600 @ 60) and since leaning out the carb a bit I get about 16.6 MPG on the highway running between 60 & 70 MPH.