So these are 15-20 year old trucks at the time of failure correct?
Maybe their service life is nearing end, remove and replace with OEM may still be the right move if it fails and don't want or need locker.
Wondering if this is good preventive maitanance to add to the common fail points such as alternators, old ignition coils, starter, cv axles, heater tee, etc.
you don't want this happening in middle of nowhere cutting trip short and causing headaches.
Yes, but I feel like diffs shouldn't just fail during routine use at 15-20 year mark. I think this might be one of the newest 4WD vehicles I've ever owned, and it's the only one that's had a diff explode after nothing extraordinary. But obviously service items vary by vehicle, so maybe this is in fact just something that should be refreshed routinely in these.
OEM refresh is probably a good idea for someone who never wanted to do anything even potentially hairy, but going new OEM means either new diff assy (which, at $1400ish when I checked last week, is a great deal) or new guts plus labor to set it up properly, with probably a price tag of around $950, if you're only replacing R&P.
Re. the new diff, I understand Toyota was/is notorious for setting these diffs up on the loose side, allowing more flex than necessary, and even more flex as they get several hundred thousand miles on them. So a rebuild of your existing unit by an expert who'll be super-finicky with tolerances might be better.
For those who've broken theirs (like me), for another $1100 (over new OEM assembly) or $1600 (over rebuilding existing unit) you get an e-locker worth $1400 and labor on a rebuild of an existing diff. And a diff that's, by all reports, far stronger than factory, and has a locker. Sort of a no-brainer, provided the money's available.
So I think adding a locker before anything breaks (giving you an expert re-setting all, um, settings and a stiffer mount for your ring gear) might be great PM, and would (once the Eaton lockers hit the shelves) cost (super rough estimate) 1100 (locker) + $400 (build) + $250 (build kit). Not much more than a new OEM assembly, and almost certainly superior in both strength and capability.
Alternatively, you could pull your existing, non-busted assy and take it to an expert to have it checked and gear meshes and bearing pre-loads re-set, etc. . . that'd probably only cost around $500. Maybe that's the good PM move? (assuming one can even do this with gears that have worn in together over many thousands of miles--I have no idea).
