Truck is a 1975 Ford f250 4x4. All new hard lines, hydroboost and wilwood master cylinder with proportioning valve. I converted the rear drums to disc's on the Dana 60 using El Dorado calipers in a lug nuts 4x4 kit. Front are also disc's using a 1976 front Dana 44.

Got everything installed, set the parking brake to apply pressure to the disc between 3/8-1/2" movement per the directions. Bled the brakes and all seemed fine. Now here's the issue:

With the truck on a lift and running, first pump and hold of the brakes lock the front fine, but the rear I can spin with my hand. Second pump and hold the rears are fully locked. Same results no matter how the proportioning valve is asjusted.

Any suggestions or tips?

 

I had to work on my late son's '95 F150 which was previously converted to Dana 44 straight axle front/4 wheel disc and the rear braking "power" was lacking to say the least, especially with 37's. I installed a disc/disc master, removed the factory proportioning valve/RABS unit and installed an aftermarket disc/disc proportioning valve, brakes are great now. With hydroboost, you should see a dramatic change in braking performance. Not trying to place any blame but there may be an issue with the Wilwood components if everything else checks out(I.E. bled all air out of the system).

 

Yes I had the hydroboost with the original 4 wheel drums and I could lock them up with ease. The master is setup for 4 wheel disc and appears to be working fine. The factory proportioning valve is gone and replaced with the wilwood. I have a feeling I still have air in the rears. I'm gonna mess with it this weekend and see. That's the trouble with changing so many things at once. Oh well, all worth it in the end.