Camkee

I have a 92 xj with the aw4 with 270,000. I was on the trails with it a few weeks after I put her on 35s and the transmission started slipping out of gear. (I linked the video of the first time it happened. Yes I know I had it coming.) It would slip out and grind gears when I released the throttle. I was able to limp it back home by putting it in neutral before I took my foot off the gas and it would shift into gear with little to no problem. The fluid was pretty dark and smelled a little funny but it wasn't potently burnt. There was a fine film of metal shavings in the trans pan. The t-case fluid was darker than usual but no shavings and no funky smell. I definitely anticipated issues with the trans/t-case after I put the tires on and figured Id have to replace the trans not long after but just wanted to get some different opinions. Anyone have an idea on what exactly is causing this? Trans or t-case? I'm assuming I'll have to replace one or both but wanted to make sure before I spent the money. Also, any suggestions (besides gearing, thats already in the works) on how I can prevent this from happening to the replacement?

4.3L XJ

I think that is the trans. It doesn't sound like a transfer case failure. However when you take it apart, open it up and check the chain just for giggles

Camkee

Will do, thanks!