Don't have a full diagnosis yet, but suspect I utterly failed in my first rear diff rebuild.
Friday morning I was on my way to meet my Upstate folks in the GA/SC/NC mountains for a 3-day weekend. After running up I-85 to the stateline and then Hwy 11 to Walhalla, the plan was to meet up with them along the Chattooga river near Burrells Ford. I was just getting on the first gravel road and threw it in 4HI (just to disengage VSC and make it mo' fun). About 4-5 miles in and doing about 25mph... suddenly rear wheels lock up, screeches to a halt. My first thought was gravel locked up a rotor, but couldn't be...both wheels locked up at same time. I get out and look around to see if I scattered any parts/debris on the road behind, but nothing. I crawl under and look around, nothing obvious. I touch the rear axle housing near the fill plug and it's on scalding hot. FML...my best guess is that something I did during the diff rebuild was not right, although I've already put 1000+ miles on it and had just dropped the break-in fluid with no evidence of something awry. It had new fluid that was a week old. Then I suspect that the tcase nuked because I was in 4Hi when the rear diff seized. Nothing was leaking though.
I haven't had cell signal in the last 45 minutes, so I hail my friends on the Ham - who are miraculously within range (another 4-5 miles north of me). In the meantime, I cycle through all possible drive modes and find that in 4LO, 1st gear I can barely move the truck forward. I can't seem to get it back into 2WD, and everything in the drive train feels like it is bound up. I get it to a better spot on the side of road and park it. The cavalry arrives.
Marshall says to me, I gotta come through Atlanta this coming week anyway, we'll get it towed off the gravel and I can pick it up on Tuesday. Woo hoo! We pile my gear into his truck, empty the fridge into his cooler and head to Cashiers, NC to look for cell service. Not much signal but enough to find a tow company in Walhalla, SC that will have a driver available "soon". That put us in standby mode for a couple hours and the rest of the gang powered on to our camp spot for the night.
Rollback truck arrives and I tell him that he's going to have to drag it onto the rollback because it won't move easily on its own. But after 2hrs of cooling off, whatever seized earlier is now free and I'm able to drive it onto the truck bed. Something is definitely grinding, but sounds like tcase to me, not the diff. Doesn't really matter, both will be replaced. I'll just be curious to open the tcase and see what it looks like, well same for the 3rd too.
I've been restocking my spares department recently and have a rear DS on its way to me already from a totaled 100K odo FJ on a parts lot. Called them back this morning and they still have the tcase and front DS so ordered both. I'll probably just get a rebuilt diff from ECGS and send them my roasted one for core.
DON'T FREEAAAK OUT, THIS IS JUST THE .......
Donor vehicle...
Mine on the rollback tow, Burrells Ford Rd . . . .