lock the rear wheels with the ebrake and see if there's ANY slop in the rear ujoint needle bearings in the cross. Wiggle the pinion shft up/down/sideways and see if there's play in the bearing.

Total gear backlash at the pinion flange should be under 1/4", i.e., you can turn the dust cover over the bearing that much.

Setting pinion height is the most critical and difficult task on a diff. I would not try it without the special mitsu tools or a fully equipped driveline shop. And I've never seen one go bad on a lubed diff in a Monty/Raider.

Not responsible for advice not taken...