its kinda strange problem,brakes seem to work ok i can run down the road and make a hard stop and i can hear tire squeal a little,i do this a couple times and rotors getting hot,so brakes are working,i put my truck in reverse and reverse solenoid clicks,here is the problem, i can unplug my plug from my truck and back up my driveway (kinda steep)and brakes do not lock up every boat i have had the brakes will lock up if you trying backing up my driveway with plug unplugged,not this one what do you think the problem is,kinda strange maybe air in system but brakes seem to work fine except backing up hill thanks for any help,it sure dont act like needs bleed