I am not wild about the teflon shims as stated in that link. I tried this and had wobble that was unacceptable so I stick with metal shims. Any size shim rings you need can easily be found at
www.McMaster.com. I got the original instructions I used for shimming diffs years ago from someone on the TRX forums. It also had notes about shimming the pinion gear which helps a lot as well. Sometimes there is a lot of front/back play in the pinion gear against the ring.