Things learned from ripping apart (to the empty case) and repairing the rear differential on an '02 Suburban....
- Yes, they used a case spreader when they put the chunk in and shimmed it. You don't have one. While you probably can buy one -- maybe -- for those particular rear ends they're not "all over the place" as they are for some common Dana units. They're not cheap either. You can make one if you want to out of (quite-beefy) bar stock if you have a welder and are willing to fabricate it. This appears to be a sort-of insoluble problem but it isn't. You see, with reasonable preload on the carrier you need only get it lined up with the shims and, with the shims properly in place, the carrier has to go far enough in that will it go straight and the cap bolts engage. You can then "walk" it in just like you walked it out. Note that if the chunk comes out "easily" the preload was wrong -- far too loose -- on the carrier and either the bearings are badly hosed or whoever was in there last did it wrong and if it was run that way for any length of time you almost-certainly have a mess.
- Make very sure you keep track of what goes on which side and direction, especially the shims! If you're not changing the ring, pinion or chunk you must put them back exactly where and how you found them or the clearances will be off. Stay organized in terms of what comes out from where and in what orientation; it all matters.
- If the gearset and chunk are ok and you don't want to replace them putting the shims back exactly as they were, assuming those parts are serviceable, should leave backlash and carrier preload within spec. In this case it not only left it in spec it resulted in backlash exactly what it was (literally, to the thousandth) before I took it apart. Ditto on pinion depth and thus engagement. Yes, it does go back together within a thousandth. Not kidding.
- Cleanliness is a big deal, just like any time you have a valve cover or oil pan off on an engine. Cover everything when its out and cover or clean-shop-rag stuff all open points when you're not actively working on them. Make sure you pay attention when putting things back together of course so you remove all said shop rags. No, I didn't make that mistake but I've seen it and it can be bad. If you find metal damage either find the pieces or clean everything inside and sweep it much like you'd run patches through a gun. If you leave any sort of trash (or worse, anything hard and metallic) in there you'll probably be doing the job twice.
- If the above on chunk, ring and pinion re-use is not true buy setup bearings. Just do. Yes, they're $100 or so. Buy them anyway. The $100 is cheap compared to your time to take a new one and hone it out yourself, assuming you have the equipment to do so with sufficient precision (Hint: You probably don't.) You will be taking the carrier in and out several times and getting the pinion inner bearing off without damaging or destroying it is a crap-shoot no matter the tools you have because the design on these typically has no rear relief via which you can get a puller on it that will bear only on the inner race. $100 spent means you will swear a lot less and, more-importantly, you will not be tempted to accept marginal fitment of something when you shouldn't.
- Sometimes the new-fangled tools work, sometimes they don't. The old-fashioned way always works. Specifically I waited an extra two days for a tool that allegedly could pull carrier bearings without destroying them. It did pull one. The other? It destroyed it anyway and thus out came the dremel to finish it the old-fashioned way (cut the inner race until almost -- but not quite -- through and hit it with a cold chisel to fracture it, thus relieving it off the shaft.) Was the tool worth it anyway? That's one I probably should have just said "ah the Hell with that" and grabbed the dremel immediately. I ain't recommending that one as 1 for 2 is not an admirable record.
- Don't try this (or other things where you really ought to have one) without a shop press. There are folks who tell you that you can heat the bearing in the oven and chill the carrier or pinion (e.g. in the freezer, or using dry ice) and it'll work. Maybe. But if the bearing does not seat completely -- by so much as a thousandth -- you're in for a bad time and see above for the fun in getting it back off.
- If you change one bearing, change all of them except perhaps the axle bearings. Always change the axle seals; they're cheap (about $20 for both) and easy to replace with the axle out. The carrier bearings and races looked ok. The one that I destroyed trying to use the new-fangled tool exposed the inner race of that one, of course, which while it wasn't dead was headed that way. I had contemplated not changing the carrier bearings based on inspection of the rollers and races but am glad I did; I would have been royally annoyed if I had to take it back apart on short time. The axle bearings are more-complex; you typically want to change both bearing and the running surface since they wear as a set which, in that case, is the axle as there is no inner race; the bearing runs on a machined surface of the axle itself. The bearing is reasonably cheap, the axle is not so much. As such unless you see evidence of damage I would not do the axle bearings and didn't. R&R on the axle halves is a trivially-easy job and a pair of axles and bearings is north of $500. If they need it then they do, but if not leave that alone.
- Your breaker bar is not long enough. Trust me, it isn't. Specifically for the pinion nut, and while its fine to rattle it to get it off it's not fine to do so to put the new one on, because the crush sleeve crushes exactly once so you must sneak up on it. If you go too far you get to take it all apart again and buy another sleeve. So yeah, that has to be done by hand. And its a lot tighter than you think it might be.
- To go along with the above spend the money on a locking tool for the yoke. Best $25 I spent on a tool for this job and it'll work on virtually any other yoke on anything ever again. You put a couple of the yoke cap bolts in with a nice washer under them, tighten it up and it has both 1/2" and 3/4" square drive holes; insert wrench handle, put pipe on end if necessary, brace it (e.g. against the floor) and crank away. Easy-peasy. Without it? Hoh hoh hoh good luck.
- Don't buy cheap bearings. Koyo, Timken and there's a well-respected place in South Korea called Iljin; all three are used as OE by car and truck manufacturers. Any of those is ok and all mark their product. Do not put Chinese garbage inside or on anything important where if it fails it is hard to change or can trash something expensive, ever, period. Yeah, I know a quality kit or piece-by-piece they cost more -- like twice as much. Spend the money. If you find a "good deal" on any of the above three do not believe for a second they're not counterfeit -- they probably are. And yes, this means do not even think about buying parts like this off eBay or similar. Ever.
Oh, and yes, a reasonably-competent schlub can indeed do this sort of a job in their own garage. Its not rocket science and the specs are readily-available in terms of preload and backlash, so its simply a matter of paying attention and doing the work.
I still have the original ring and pinion (albeit both in good condition) and roller-locker chunk in there. If I had to change any of those I would have almost-certainly bought a posi chunk instead, simply because they're little if any more money, and the ring and pinion are a matched set so if you change one you must do both or the new and old will destroy each other. Somewhere down the road perhaps one of those will go bad and I'll get to do this again -- and if so, I'm properly armed to take it on, so there you have it.
Onward and upward.