Grinding going from neutral to 4 hi

I have a 89 Cherokee Laredo with the NP231 transfer case. I have only owned it for a couple of weeks, in this time I have not driven it, I was doing various repairs one of which was the replacemnt of the hub assembly on the right side. I drove it for the first time yesterday around my backyard and shifted into 4h then neutral then to 4L. I came to a stop and shifted the trans into neutral and the t/c back to neutral then tried to shift to 4H,I got some grinding noises when I attempted this. I went back to neutral then repeated the process, more grinding. Tried once more and it finally went in to 4h. Then it was very difficult to get back into 2H.
Any one have any ideas,suggestions, comments,instructions?
Thanks for any input.
Scott

check for craked or broken vacuum lines from the transfer case to the front axle disconnect.