Last summer I did a major overhaul (engine, clutch, transfer, etc.) to my '99 manual transmission LS S-10 truck & everything was working fine. Now I've noticed that it can go 4X4 hi or low forward but when I shift to reverse it spins from one tire (it doesn't go 4X4). If right then I shift to 1st gear it takes off in 4x4. How can this be?.