I'm not sure what i need, i look at places like thunderracing and they have 2 different things for each set like motive 3.73 ring and pinion which is under 200 and they have the same thing with the master install kit for over 250 i think.... Do i need the install kit or is the ring and pinion what i need?

 

You will need the kit. I would recommend GM superior gears for running quiet.

 

What is the reason that i need the install kit????

 

The install kit will contain a crush sleeve for your pinion, shims, bearings, gaskets, and new bolts for your ring gear.