does a 1975 chevy pickup 2wd has a proportioning valve? If so how does it work and the signs it is bad? my truck has disc/drums brakes?
Yes The valve causes your rear brakes too apply before the front brakes .Safety reasons,(If your fronts apply first chances are the rear of the vehicle could come around on you) It utilizes spring pressure and offset valving. There is a rubber button that you must depress to bleed the rear brakes It's an override.
Yes they do go bad! It sounds like that is your problem. You can try bleeding the proportioning valve with a brake bleeding gun, making sure to open every valve then re-bleed the brake system this will eliminate the possibility of a air bubble in the proportioning valve. I have changed probably ten or twelve of these things in my ventures.
