Stock XJ grinding/popping in 4wd

[GasHogg46]

NOt sure if anyone else had this happen, but my Jeep pops & grinds in 4wd. Not long ago, my Jeep started making a grinding noise in 4wd. Didn't get much snow, so I didn't use it much. About a month ago, I got a humming from the front. I changed the front diff gear oil on sunday. The humming is still there, and the grinding is 100 x worse! I was wondering if this was a failure of the u-joints, or something much worse? It sounds like some serious metal on metal action! I'm no mechanic, so I'm not sure where to start

[4.3LXJ]

Check your front wheel bearing. They grind before they go.

[LizardRunner]

I'd be betting with Steve on this one. I had that same thing start on da lizard and ended up just replacing all four corners bearings just to be safe. I've looked at two other XJ's lately for the wife and passed on them because they had bad bearings. I figure if those are shot, then there are other important parts that have been neglected as well.

[nickxj94]

Humming would be hub assembly, that metal to metal grinding better check your brakes also lol

[XJ4IV]

does the sound go away while in 2wd? if so its your transfer case chain! not a total PITA but will give you a run for the money... I bout a replacement at autozone for like 81 bucks which was a mistake! they only backed it for 90 days... well the POS lasted like 100 days... next one I got from a JY vehicle I just located one that looked like it had been in 2wd forever and went with that one... its still in there as far as I know as I switched to a 231 t-case last year!
really wont need anything special for the swap just a good snap ring removing tool the one that open a ring wider and then just atf4 transmission fluid to fill her back up!... if this is the route your wanting to go I will give you a very easy step by step on how to do it if youd like!

[GasHogg46]

does the sound go away while in 2wd?

Yes, it does not pop or grind in 2wd.

[XJ4IV]

then thats your case chain... cheaper and a little easier than a wheel hub!

[Mudderoy]

Yes, it does not pop or grind in 2wd.

Sounds like a stretched transfer case chain. The chain itself is about $110ish, but I learned the hard way that you need a rebuild kit and new driven and drive gears, otherwise you'll be replacing the chain every 9 to 12 months.

[XJ4IV]

I bought a WHOLE NP231 case from a junkyard for 150... pick and pull, I had the NP242 which is a decent setup but I wanted the 231 for ground clearance since the 242 sits about 2.865 inches lower (round about figure) the 231 for some reason holds up better not sure why or how but Ive NEVER had an issue with a 231 and had MANY problems with a 242 (seals oil pump output shaft speedo gear chain... chain chain, and a shift lever inside the case kept popping out of 2wd into neutral)
my .02cents saying all that to say... might be cheaper to get a 231 from a JY.. and if that IS the 231 you have ... just do what muddy said...