ok i have had this problem for a long time now and its getting worse. when i first start my truck and take off i have to get it to 2000 rpm or higher for it to shift into 2nd. sometimes it wont shift into 2nd even if i got to 3000rpm but after it shifts its fine i can stop and it will shift through first like nothing was ever wrong what could this be please HELP.

 

sounds like a valve hanging in the valvebody or a delayed engagement due to slack between the clutches or low fluid pressure
have a trans shop check your throttle pressure adjustment or any of the above