Tran. help.

[rcktman]

I have a 1997 f350 crewcab with 164,000 the motor is stock as far as I can tell. The guy I bought it from said the trans. was replaced less then a year ago. Here is the problem about 50% of the time it shifts from 2nd to 3rd fine, the other 50% it slams in to 3rd gear. This is under normal acceleration. If I am hard on the pedel it shifts fine. The other thing it does is if i tap the brakes it disingages the trans. If i am crusing at say 55 and tap the brake with out letting off the pedel the rpms go up. Any advise would be great.