I have an 2004 dodge 2500 diesel, maybe a couple times a week or so and usually under really light acceleration, like when turning a corner and starting
down the street, my gas pedal gets really stiff and the truck wont shift. Now if i let off the gas pedal and accelerate again sometimes it changes back
to feeling normal, but other times the gas pedal remains stiff and the truck wont shift, so I just punch the pedal to the floor and then it shifts, Any ideas of what it could be!!

 

Check the TV cable that runs from the engine down to the drivers side of the tranny. It hooks to a lever and controls pressure and shift points for 1/2 and 2/3 shifts. Make sure it seems to be functioning freely (you should be able to move the lever by hand). Also, have someone push on the throttle and then see if that pulled the cable to move that lever the full travel. If there is still slack, it should be no more than 1/4".
Don't know if this will help you find your problem, but it's a place to start.

 

Sounds like you need to replace the gas pedal with an accelerator pedal

(Ok, I'm done being a smarta$$ now)

 

I'm confused, is this with your Cummins DIESEL or with another Gas Engine Vehicle???

I know what your saying. Sometimes the cables will get stiff. If you can or have a cable luber, lube it up (commonly used on ATV's, dirtbikes and stuff, cheep) Sometimes when you twist the frame, or move something, which happens in turns ect, the cable will do that. Most likely just needs to have some oil run down in it and you'll be good to go. It's amazing that they just now are putting the TPS inside, I mean why run a cable to the motor, exposed to the eliments to drive the TPS???? It's amazing