Well, when you have the T-case off, check the splines, coupler and transmission output "play" on the transmission side. I would push IN/OUT HARD with my hands on the tranny shaft to see if there's excess movement. Could be a thrust washer in the tranny failed...as unlikely as it seems (otherwise you'd probably notice some tranny issues). If the coupler to the transmission is sloppy, I'd replace it. Ensure the output bushing on the new T-case is good. The driveshaft should sit in there fairly snug. I would check the driveshaft for being bent. You never know. A buddy of mine used to own a junk yard and sometimes he'd lift someone's car/truck up and move it if they parked in the wrong spot. But it sometimes bent the driveshaft a little. So he had to stop. The owners never new. And of course, check the pinion, etc. There was an issue on these Rams way back when, some sad owners, ...the Pinion nut working loose. I'd probably pop off the cracked rear cone on the old xfer and do an autopsy. I bet you see the problem. I bet if a guy cleaned and JB-Weld..the entire joint...I'd love to see how long it would last. That would be the ultimate test. I bet it would surprise people.
I would be inclined to check the play on the xfer case rear driveshaft output bushing ....and probably order a new one & change it, unless it's nice and snug. There's a nifty
Spent-More ..I mean, Kent-Moore tool the dealer should have which makes replacing the xfer output bushing (and a tranny bushing) a 5 min piece-of-cake job. *Looks* like
below. That would tighten the driveshaft up. If you walked through the back overhead doors, just walk in, around closing time ...with the xfer case in your hands, wearing your dirty duds, bushing in hand (buy it from the dealer so you can say you got it there) ...a mechanic might just change it right there on the spot. Give him $20. I mean, we're talking a small family-run dealer here, ...not a big one. Our dealer has lent me the tool before, if I bought the bushing from them. Wrap 2 coils of masking tape around it though...the sharp machined edges can actually mar the new bushing.
Oh...and stop doing reverse-to-low's! LOL
(just kidding)
.