changing gear ratios iin 8.25

Its been a little while. Well basically it needs to be setup about as percise as you would put your engine together. There are caps that hold the differential in place, that are location/direction specific (like main caps). Those caps hold the differential bearings in place, each bearing will have a shim behind it. That shim will adjust your gear backlash for your ring and pinion. Pinion. Pinion will have a shim behind the bearing that needs to be pressed on. This will give you your pinion depth into the ring gear, important for teeth pattern. behind that goes another bearing, then your crush sleeve. crush sleeve gets squished to a certain point to set preload on the bearing. Checking that preload on the bearing is turning torque.

http://www.moparmusclemagazine.com/projectbuild/5148_custom_rear_end_install/

Its not quite a job for someone new to do alone. Very very wise to find someone thats done it, right, and watch.