well, if my brakes are on the turn signals won't work,(just stays solid) but if the brakes are off then they work fine, also if my tails lights are on (work fine) but once i turn on the blinker the both flash like hazards.
So does your truck use the same wire for turn signals and brakes stock? Or did it have seperate wires? If it had seperate wires you have to buy the turn signal adapter thing made for trailers. You can buy them at most auto parts stores in the trailer light section.