I got a 1990 2 door 4.0L Jeep Cherokee, I went to 4 wheel drive today I fond 2 problem.
First, shift from 2wheel drive to 4H and 4L is pretty smooth but the gear will jump out from 4L usually.
Second, my left rear wheel got stuck in the mud, so I shifted to 4 wheel drive but no metter 4H or 4L only left rear wheel spin and the car won't move forward even there were 3 wheel on the hard ground, I can feel very very little power from front axle, I am sure 4wheel drive is engaged but I don't know why the front wheel can't get power.

What should I do to check the 4 wheel drive system, never work on jeep before so please give more detail ! Thanks !!!

 

Transfer cases are pretty straight forward. Try the basics first like is there a front drive shaft? do you hear any unusual noises when in four wheel drive? The linkage could be off but you would more than likely still get in 4 wheel drive even if it was a bit off.

If not you should check the fluid in the transfer case or is there any leaks? does the transfer case look wet? is the case cracked?

Other than this your best bet would be to open it up and see how it looks inside. They are very straight forward

Also what transfer case is it? Either the NP231 or NP242 since u didnt mention anything about full time my guess is NP231.

Here is a link on how to open up an np242 (just about the same procedure for the NP231)

http://www.mallcrawlin.com/forum/showthread.php?t=8549