93 transfer case

Hey evryone.... I have a 93 s10 blazer with the tahoe package... well im 99% sure that the transfer case is shot... first of all in order to put it into 4 wheel i have to put it into (N) then push the 4 wheel button then put it back into (D)... i can hear all the relays click and i can hear the case ingage if i open the door and listen real close... well once its in 4 wheel and i give it gas the truck barely mooves.... it dont matter weather its 4 hi or 4 lo... so basicly i was wondering if anyone out ther might have a transer case for sale ? Or has anybody had this problem and if so what did you do ?