I have a 91 f350 4x4, I've done a dually conversion using a non-rabs rear axle. i eliminated the rabs valve, and installed an adjustable proportioning valve to the rear brakes. Before the conversion the brakes worked fine. after the pedal is firm at first then goes down slowly like the master cylinder is bypassing internally. I've thoroughly bled the system. My question is are there differences between rabs and non-rabs master cylinders. You guys have always come through in the past with my other projects. i hope some can help. Thanks!

MARC

 

Bleed the system again. Sometimes its just not enough.

 

that's my next move, I was just wondering if the two master cylinders were different internally. thanks for the reply.