RESQ1
RCMC is correct, the next logical thing is to check the tv cable adjustment.
this can get a little complex, the simpliest way to start out is
1) With someone in the cab , engine off, vehicle in park, have them step on the throttle completely to the floor,
the tv lever at the transmission should have approx. 1/8th" - 3/16" of play left.
In other words you should be physically able to move it by hand at the transmission.
This is a VERY GENERAL and simplified instruction.
A lot of people have the habbit of moving the kickdown cable adjustment (tv cable) forward, (allowing excess free play at the transmission) resulting in lower line pressures to achieve desired wide open shift points.
The next place you would check is your governor solenoid, which is located in the pan, (96 and later dodge rams only).
Bill Kondolay
Diesel Transmission Technology