If you use a smaller pinion gear you will ease the power required to move your truck, effectively increasing torque, or making it easier to move your truck with the same torque the engine already has.

You will lose top speed as a result of using your engines peak power earlier on the gear ratio.

You can increase your torque by tuning several areas or mechanics in your engines air flow, port timing and other things.

I hope that helps some.

good luck