Rear brake control

[JOAT/MON]

I am building a 1970 1 ton dually from the frame up. The front and rear axles are from an 89 Sierra R3500 2 wheel drive. The 89 had a lever attached to the differential housing, that moves a valve of some sort in the line to the rear brake wheel cylinders. Does anyone know what that valve is supposed to do and would it matter if I leave it out? I have owned several other trucks and they didn't have such a device. The rear brakes are 13" drums with 3 1/2 wide shoes. The fronts are disc with the 89 hydraboost and master cylinder.

I'm wondering if the rear wheels will tend to lock up ahead of the fronts in a panic stop or on wet roads. I intend to run this truck on the freeway at or above the limit and often pulling a frieght trailer so good braking is very important.

[brantjs]

I'm not familiar with the vehicle in question, but from what you are describing that is a proportioning valve. It ties in so that it determines when you have more weight on the rear and will transfer more of the braking power to the rear of the truck. I'm not smart enough to tell you if the brakes will or won't work right without that valve.