Transmission problems need help??
 

I have a 2006 2500 4x4 Dodge 5.9liter cummins with a 4spd auto transmission. The transmission Is acting up bad and I dont know wat the problem is. Wen I put the truck in reverse it won't reverse. But when I put In drive it will move a little bit but I have to get the rpms kinda high. I need advice bad thanks.