Usually when driving highway(not always) the 4 x 4 selector dial is on 2HI, the selector dial lights start flashing and then the light goes to 4LO sometime Neutral and you feel it slowdown a lot, after that happened it wudnt go in reverse, until I put it in drive , then neutral let it roll and switch it back to 2HI, then a cluncking noise sounded and it was back to normal....Service 4x4 light went on only once in the past but it wasnt acting up....