ever since i got my truck, it has jerked really bad going from park to rev or drive.... then when your going down the road and the truck downshifts it will jerk... this morning when i got into it, i put it in reverse and it wouldnt do anything... i mashed the gas more and it caught and spun the tires and backed up... im not sure exactly what is wrong with it but when i put it in drive it drives ok, it just seems like its starting off in another gear or something... what could be wrong? if the tranny has went bad does anyone know where i can get one at a good price?