which gearbox diff combos to take.

[harry b]

I've been searching a bit for the ideal gearbox diff combo on my car.
I have the HPC with a very torque vauxhall engine, somewhere in the 230+HP and a bandwidth of 2500-8250rpm. Real power kicks in around 6400.
Current diff is 41/10, and I've got two of them with LSD. (one spare)
Current gearbox is a sierra.

First gear now runs towards 40Mph, and the step from 4th to 5th is just dropping 400rpm too much to be able to pull in fifth beyond the 6800 rpm.
I would like to have the first gear to pull to 65Mph

Above is with the use of 16"HPC wheels, I've got the 13" R500 wheels too.

Precalculations shows I need a 2.3 first gear ratio, 0.95 5th gear and a diff of 3.6.
Anybody got suggestions??

[johnny7]

To have it geared to get to 65mph in first you may find you"ll go through your clutch pretty quickly getting it off the line.
My hpc 215bhp/3.92diff/13"wheels/bgh E6 2.75 first/ about 45mph in first--nice balanced power delivery.
john