Hard shift first gear

[easttexaspowerstroke]

Hey guys my ride is a 2000 F250 with the 7.3L. I just bought it from a friend and i knew it had a rough first shift, he said that his mechanic told him it was just a sensor that needed to be replaced but he never did it. If anyone can offer any suggestions before i take it to a transmission shop i would appreciate it.

Truck starts off and you can feel it "slip or stall up" and shift about 300RPM LATE then shifts hard (depending on speed) the faster i go the easier it shifts. If i put the pedal to the floor it will shift normally. I don't believe the transmission is having problems because every other shift is flawless and smooth. Just first to second. Again i appreciate any input thanks guys!