Trailer back feed

i have a 3axle trailer and a gmc dually that has factory trailer brakes and a tow haul feature and somehow when hooked to the trailer i am having transmission control modules go out and the truck doesn't know what gear to b in and it has to b replaced is anyone else having the same issues pls help

 

That's odd Try installing diodes. You can get them in whatever amp rating you need. You could install a stand alone brake system controller. I have one it works great.

 

Nope. No problem with mine. What year/engine? Have you taken it to the dealer for diagnosis? Might want to have the dealer involve either their TAC department or a Field Engineer. Sounds a bit weird.

 

Check for a GOOD ground on the trailer......