Quote:
Originally Posted by frnkeore
For a light car, say a '27 T, 1500-1800 lb, the -238 trans with 411's and a 400jr cam, would be a real terror. Thinking out loud 
Frank |
Don't think you would like that combo, truck gears just don't cut it in a high performance application. The hole idea of close ratio gearing is to keep the rpm spread to a minimum. The move to 4 and 5 speed transmissions is for the same reason.
There are some rules of thumb for gear 1st gear to rear axle ratios (there are other factors, these are just starting guidelines).
Drag Racing: 10 to 12
Street Performance: 8 to 9.5
The truck gears
3.35 1st gear X 4.11 rear axle = 13.77
3.35 1st gear X 4.55 rear axle = 15.24
Even with a higher rear axle ratio they have a high final drive ratio
3.35 X 3.78 = 12.7
3.35 X 3.50 = 11.7
3.35 X 3.25 = 10.9
And you still have the gear spread issue.
Now the stock 39 and Zepher gears
Stock 2.82 X 3.78 = 10.7
26T 2.33 X 3.78 = 8.8
25T 2.12 X 3.78 = 8.0
Now the stock 39 and Zepher gears with a 4.11
Stock 2.82 X 4.11 = 11.6
26T 2.33 X 4.11 = 9.6
25T 2.12 X 4.11 = 8.7