i had the same problem after i bought my truck the first thing i did was put my detroit and gears in and after diconnecting the rear brake lines i had never had rear brakes for like 6 months. tried 3 different LSPVs (used) none worked. so finally i just plugged the rear brake port on my master and ran all 4 of my brakes off the front brake port. its been working perfect ever since. only problem is if any brake line goes out there all out
