I can turn the truck on, but when I put it in drive, it won't move. What could the cause of this be?

 

Does it start to jump forward like vehicles normally do when you put it in gear? If not i would check the cable that puts the transmission in gear.

 

Torque Converter, Flywheel, Transmission, Rear Gear...

 

this might sound stupid and 'duh' sounding, but maybe the ebrake might be stuck on? as in rear drums locked up.. I see you drive an automatic though and not many people use the ebrake when parking them.. I hope it's something simple or you have warranty left! Good luck.

 

first of all welcome to R-F. 2ndly, a lil more info on yor truck would be helpfull. yr, auto, 5-speed, 2wd, 4wd, mileage, etc....

 

possible bad EPC in the trans

 

Take it to the dealer. I think there's two threads? Either get a truck inclined friend to help you or take it to a dealer.