What gear ratio?
 

I thought I would change my gear ratio for next year. I need help with picking the right ratio. The car weighs 3200# with driver, BBC, turbo 400 with a brake and Dana 60, a 14-32 tire with a 101 rollout. The engine made 621 HP.@ 6100 RPM and 621 TQ. @ 4500 RPM. Also can someone shed some light on what rpm I should be shifting at? Right now I am shifting at 6400 rpms. The car runs 10.02 @ 132 Mph. with a 4:10 gear. I hope this is enough information thank you for the help.

Re: What gear ratio?
 

What do your RPM's drop to at each shift and what is your trap RPM?

Re: What gear ratio?
 

Assuming that you have a standard TH400 with 2.48, 1.48, and 1.00 gears, according to my calculations you should run 4.56. That should have you crossing the finish line right at about 6400 RPM. (Right now you are crossing it at about 5700)

SLR 11.3088
Gear Ratio: 4.56
Tire Diameter 32
Shift RPM 6400
Weight 3200


RPM after shift

Shift RPM 1 - 2 2 - 3 3 - Max
2000 1194 1351 2000
2500 1492 1689 2500
3000 1790 2027 3000
3500 2089 2365 3500
4000 2387 2703 4000
4500 2685 3041 4500
5000 2984 3378 5000
5500 3282 3716 5500
6000 3581 4054 6000
6500 3879 4392 6500
7000 4177 4730 7000
7500 4476 5068 7500
8000 4774 5405 8000

MPH 53.9 90.3 133.6

Re: What gear ratio?
 

Also, I think that I would try to make the 1-2 shift at 7000 and the 2-3 at 6400. Look at your HP and TQ curves and see where your RPM's end up on the curves after the shift using that "RPM after Shift" table that I posted.