I don't remember hearing about bearing problems in the rear 10-bolts. There shouldn't be many problems, unless it was run low on fluid, or the fluid was contaminated.

Isuzu does use a crush sleeve to adjust pinion bearing pre-load. This goes between the nut and the outer pinion bearing and is a one time use item. If it squished too far, you need a new one. If you have problems, you probably need to have someone look at it. Diffs do not randomly have problems with the bearing preloads or settings. Something else must be wrong.

Good Luck,
Michael