1993 dodge truck problems?

[Luke]

I have a 1993 dodge 2500 Cummings turbo diesel. when i start up the truck and put it into drive, it doesn't go past 20 mph no matter how far i push the gas pedal. after i go about five miles it finally starts to shift right and slowly makes it way to the Speed limit. After about ten minutes of driving i don't have anymore trouble with it unless i shut the truck off and it gets cold again or i just let it idle. I had the trans rebuilt and the torque converter replaced. Please help me with this problem thanks