Rear end gears must have the proper backlash , pinion depth, and pattern on the drive side on the ring gear and the coast side of the ring gear. I dont thing just adding a shim here and shim there would be the right way to do it. Using dial indicators and the proper tools are needed. Rearends can be tricky and is best left to the pros. If you read up on proper dimensions and get the right tools you can do it , just be careful on the measurement.s