Bad Noise in 4WD

Hi all, Im new here, Hale to the Jeep :) I got a problem, When I shift to 4WD, it kinda sounds like a tire is squeeling and the jeep kinda goes a little sideways sort of, not much, just barely can tell it. Then I shift back to 2WD and it still makes the same sound for a while until, "KACHUNK" big awful chunky sound and it goes back to normal??? Any thoughts? Thanx a bunch
p.s. its a 94 wrangler

it seems that my jeep needs to be stopped to shift to 4 x 4. is this normal???? my 92 jeep could shift on the fly!!!

Does it shift ok when stopped?

Does it shift ok when stopped?
yea, when stopped it shifts to 4WD just fine!!! Someone told me that they made a few diff. front end units back in the mid 90's and some were shift on the fly and some were not. :( I just wanted to confirm, thanx for the reply!!!!

You may have a different T-case, or the synchros(or what passes for them) in the T-case could be worn. As long as everything works fine, and you're ok with stopping to shift to 4wd, I'd say drive it!