2005 v6 red brake proportioning valve ?

Hello thanks in advance.. I put all new front calipers pads and such in.. everything works great for a month and a half then coming down a Hill hit some bumps no brakes pedal to the floor ABS humming and ever since it feels like the rear brakes aren't working The e-brake works but feels like the rear brakes not working can anybody help me with this thank you. Stainless steel front lines but not the rear there's no air in the system but can't figure it out.. I'm missing something somewhere...
The rear brakes are adjusted tight the E brakes work it's just when I push in the pedal it seems they're not working the way they should be and secondly if I go over some bumps I lose all break pressure and you can hear the ABS unit humming away for a few seconds very strange thank you

 

Have you adjusted them? I believe you are supposed to turn the gear till you hear a slight rub, then back off . Does the truck stay stopped if you put e brake on then out in drive?

 

Try this: