Truck won't shift
Have a 2000 Chevy silverado 1500hd 4x4. When I left
work yesterday the truck jerked real hard when going into
3rd. Now it will not shift on its own. I can manually shift it
and it will go just fine into 1st and 2nd but slips going into
any other gear. Also in 1st and 2nd it will pull just fine but
in 3rd or higher it will only pull at a low rpm if the rpm gets
to high then it quits pulling and the motor just revs up. If I
come to a complete stop any gear higher then 2nd will not
pull at all. What happened? What could be my problem?