Hello I have a 1972 atc 90 with hi and low range, I had the motor rebuilt witha whole new top end and i was riding it today and it ran very well and all of a sudden the rear wheels locked up and it stopped with it in high range this also happens in low range. If I move it backwards it becomes unlocked up and I ride it again but it goes through all of the gears very well but locked up occasionally. If anyone can help me out I would really appreciate it.