I got to wondering in the difference in a rear end gear ratio means a proportional change in torque at the rear wheels. ie if I have a 3.00:1 rear end gear now and swap in a 4.00:1 will my torque at the wheels increase 33% ? Actually my swap would be 2.56 to 3.42.

Many thanks!

My swap from 2.56's to 3.31's was a 29% increase in applied torque at the wheels

I don't know the numerical value of the torque increase but, going from 2.56's to 3.42's will certainly be noticeable in the seat of the pants,
and also some at the gas pump! LOL!

A fairly easy way to get that number is just simple multiplication.

Engine torque X Trans gear ratio X Rear end ratio

Some of the aftermarket axle companies use this to help you determine the load your car will place on the axles so they can help you get the right ones, but I'm sure it can be aplied to check your torque multiplication for a given gear change "in the same vehicle" that is.

Rob