All right CheCk it out, a while bakC I Converted my 620's drum brakes to disk brakes in the front. I also notiCe that every body even me has had trouble with brake fade or with brake pedal going to the floor. After months of thinking and messing around with it, I finally figured why this happens, Your truCk needs a "proportioning valve" This valve Causes brake pressure to be metered throught the hydraliC system. Due to the faCt that the new front Calipers are muCh larger than the rear wheel brake Cylinders, it would oviously take more fluid and pedal travel to expand the Caliper's pistons to Contat the brake rotor. This fix is verry simple, Well sine I have gutted and disguarded my old brake lines and Components for new lines and Components, I've installed the proportioning valve on the rear hydraliC brake lines and mounted it on the Chassis a Couple of feet befor it splits off to the rear wheel brake Cylinders. Then I've adjusted everything and bleed the entire system. And long and behold the brake system now works perfiCt! YOu Can get these valves at any auto parts store, I got mine at summit, My valve has 2 funtions, one is for a manual adjustment that would be used all the time and the 2nd funtion is for drag raiCing perposes, its has an eleCtriCly Controlled solinoid that would shut off hydroliC pressure to the rear wheels at a push of a button for awsem burnouts at the traCk. CHECK IT OUT thanks for looking

Great info.

Just got my proportioning valve in the mail, I'm going to install it and take some pics for everyone else out there that is scratching their heads about the brake pedal/fade problems after the front disc conversion. Check back soon!