A friend had one of these units in a F150 back in the late 70's and it worked great, until he lent the truck to a neighbor to use while moving. It seems the neighbor ignored the instructions to let off the throttle while shifting the unit and instead kept his foot in it. The result was a tow bill and the end of the overdrive unit. I don't remember specifically what broke, but I know that parts availability was non existant. I don't know if he still has the unit laying around or not, might have to look him up and find out.