Bolts holding the ring gear on are left handed. You must turn them clockwise, as viewed from the head side, to loosen them. Put thread locker on the clean threads before installing the bolts in the new diff, use carb cleaner to get the oils off the threads. You need a dial indicator to get your .010" ring gear backlash. Get a shim assortment to work the backlash out. Once you get the backlash set you're supposed to put about .004 -.005" more shim on both sides to preload the bearings in the diff. They make a case spreader to help with the final install but most guys just pound the diff in with a heavy soft faced mallet. A set of calipers come in handy to measure the shims as you're trying to figure out your shim thickness. Setting up gears is pretty similar to doing machine work on the engine, if you don't have the right tools you can really mess things up.

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