hi I am Dan own a 93 dodge Dakota 200+ miles love the beast. well question being was told my proportioning valve was bad rear brakes not getting or getting very little fluid. Well turns out this is an obsolete part joy!! well I found a valve for a 96 Dakota and I cant find anything saying the 2 are compatible any help be great.
thanks

 

IDK how to help with that valve but I hope to eventually put discs on the rear of my 94dak. If you can here is the site. http://ssbrakes.com/

 

On the 87, and I think on the newer ones as well there is a height sensing proportioning valve located on the frame just forward of the leaf sping. The purpose of it is to limit the fluid going to the rear brakes when there is no load in the truck.
They are known to seize up and go bad. I don't know of anyone who makes replacements either. On mine, I took it off of the truck. I ran a new brake line from the proportioning valve,( located on the inside of the frame about below where your feet would be when driving. ) To the rear brake hose. I then plugged the remaining hole in the proportioning valve.
I don't drive aggressively, but the brakes seem fine without it. And I do drive in snow.......
It is more likely that this is the valve that is bad rather then the proportioning valve if you are not getting fluid to the rear cylinders. And keep in mind, even when working correctly, it restricts fluid when the bed is empty.