94 2500 had problems with turn signals. i put in a digital flasher and smoke started rollin out from behind fuse box. i went to move the truck and now i have no speedo and the truck wont shift out of first gear. checked fuse's, changed computer and prom, now it starts off in 2nd and shifts ok but runs like crap. put my old prom in and i'm back to having only first gear any know what up?

check the input speed senser on the transmission that is what controls the speedo. there is an input and an output, there the same and there on the driverside of the case. one or both maybe bad. it could be the reason why it doesn't shift out of first cause its a electronic trans and the computer doesn't know how fast your going to know when to shift gears. that maybe the cheepest and fastest thing you can try. let me know what happens if you try that

you also may want to check the ignition switch - when faulty, no speedo, check gauges light on, won't shift ( stuck in high gear) and you may have several transmission solenoid codes.