Banging in 4wd

I have a problem with my 1994 XJ, 4.0L 5sp, when I engage it into 4wd and move forward it makes a loud "Banging" sound, I replaced the two outer front U-Joints, however the rest are original. Could it be the front driveshaft U-Joints that are caked as well? or is it a possiblity that there is more wrong with it than meets the eye? I tried to wiggle the front drive shaft with my hands, and rotate it a bit, but it is as stiff as a board and will not move, is this normal? I am new to 4wding really so anything is good.

any help, or suggestions would be great

GQ

i had the same problem. your tcase is messed up. luckily, theyre cheap to replace