i have an 89 xj bought it with a 3 inch lift on it everything else is stock when you put it in 4x4 there is a bad knock coming from sounds like the front end previous owner said thats how it is but i'm not buying that I have changed all u joints in the front and front drive shaft and wheel hubs put a 6.5 inch lift on and the knock is still there when in 4x4 i dont think it has lockers because when its in the air the wheels turn in the opposite directions plus its there when you drive straght or turn anyone have a clue where to go from here i'm about to open the transfer case

 

I have a 98 and mine did the same thing but it did it all the time 2wd or 4wd it ended up bein the flywheel it was loose

 

my 89 did this! turned out my tranny mount was shot!. so take a look at that!

 

my 90 just started doing that, pretty sure that its the transfer case chain slipping