Outer Limits 4x4 Board

88'Sierra

With my braking system, I have upgraded everything to make the brakes good and engineerable.

Now i'm thinking i will need an adjustable prob valve to suit the disc rear so i can get the braking right. I just don't know where to put it exactly

A B or C Position? Anyone have an idea?

Picture shows what is plumbed up atm. Does everything seem ok?


Thanks for any help

I'm thinking position C

If the load sensing proportioning valve is done away with, A goes only to the front and B and C will be the same thing. Most people put it at B.

The original prop valve is not load sensing. It sits 3/4 down the chassis rail and nothing brake related is attached to the diff except for the brake line with sierra's. Which is rare.!

It does look like it floats around inside depending on front and rear joined brake pressure. Ive had it apart to clean

The proportioning valve will send excess fluid pressure back to the front so the rears don't lock up first.

Because it was drum rear and they use heaps less pressure, you'll need to get rid of the standard proportioning valve and and run it like I said.

Ok now i get you

Do you know if this is legal? Able to be Engineered?

Otherwise i will run a hilux load sensing prop type in the back

Got hold of engineer.

Don't have to run the lux type bar load sensing. Its not a commercial vehicle.

Adjustable valves are engineerable.

Going to run Blue A line for front only

Red B/C line for rear only

The master is suited for discs anyway. All he said he is looking for is the front to lock up before the rear.


Thanks for your help 91mav. I just needed it confirmed through engineer.