Im far from an expert but something that may be dumb enough for me to think of might be too obvious for the others to think of...
So its all good in 2wd on the road, but when you go off road and change to 4wd things lock up and the noise starts?
I know mine struggles to get past the part time 4wd setting (orange) down to the full time setting (green) without me doing a little dance with the gears and rolling back and forth etc - the locking up and noise could be a sign you're getting stuck in part time too?
Way too obvious? If not, read on. If yes, ignore this and have a moan about newbies piping up when they should keep their un-knowing mouth shut
Other makes refer to Part Time and Full Time differently to Jeeps which can lead to confusion - In a Jeep Part Time means you'd only use it Part Time and Full Time means you can drive around with it on all the Time - not Part Time as in you can drive around in it all the time and it will activate when necessary, or Full Time as in constantly in 4wd. Lets not go into which is right, just understand that Jeep does it the first way. Unless you're in really slippery loose stuff, Part Time will make your wheels grip and slip and grunt and pop - especially when trying to turn (if you get stuck in Part Time 4wd on the road - try not to do any turning
).
Way too obvious?