sqeeking 4x4 93 trooper automatic

Ok so i just bought this 93 trooper has just over 160,000 miles on it...took it out last night to really test 4x4....I have used 4x4 high a few times last week...very pleased tell last night when I put it in 4 low for the first time...now my 4x4 high and low are sqeeking very loud!!! Any thoughts on this!