I am sick of working on my brakes. I can’t figure out why the rear does not work worth a damn, neither can the shops I have taken it to. I am thinking about ripping out the stocker proportioning valve and installing an adjustable. Will I have any problems with my rig still having drum brakes on the back and can I hurt them but letting more pressure go to them? I have replaced every thing in the brake system but that and have had no luck. I am going to start towing a trailer soon and would love to have functioning brakes for it. Thanx for the help.