I thought I just finished with a rear disc conversion on my Sunny truck (minus the emergency brake cables) but the rear discs are dragging after bleeding the brakes. All calipers, rotors, and master cylinder came from a non-turbo S14 Silvia. There is some sort of valve in the rear line before it reaches the rear diff and splits off. It's near the back wall of the cab, inboard of the frame rail under the bed. This truck came with front discs from the factory (1991). Is that residual valve that makes the drums work correctly because I thought that was incorporated in the master cylinder.

does the valve you are talking about have a rod that connects to the diff?

some utes(not 1200s that ive seen) have a valve at the back to control the rear brake pressure then the car is loaded up, or if the rear lifts up to much or something like that

residual pressure vavle is usually in the master cylinder, but the later utes ran a different master cylinder to the early ones so it could have the valve elsewhere

yeh the valve pig is talking about is the load proportioning valve, it varies the rear brake pressure by the amount of weight you have in the back

Yeah I originally thought it was some kind of load proportioning valve, but it's not attached to the suspension any where. I never gave it much thought until now.

then it probably is a residual pressure valve. unless the front circuit goes through it as well. then it could be a bias valve

Sunny Truck has no load-proportional valve.

It is a standard disc-front brake valve, just like the coupes have.

If the master cylinder was originally used with rear drum brakes then it will have a residual pressure check valve for the rear brake circuit, in the master cylinder.
It should be removed for use with disc brakes.

The front circuit doesn't go to this valve.

@ ddgonz - So is the disc-front brake valve pretty much the same thing as the residual pressure check valve, and needs to be removed?

@ dodgeman - The new master cylinder is from an S14 Silvia, same car I got the front and rear calipers and rotors from. On a side note, it bolted right up to the late Sunny booster and has the same plunger depth.

the late ute master cylinders were the same style as the s14 master, just like skyline ones

Hmmm...there is a weird valve there about half-way back

* 46400-G1500 VALVE ASSY 8910-

The name is helpful
maybe it is a load-sensing valve...