This picture shows the internals of the stock TJ/XJ proportioning valve. We’ve pulled the bleeder screw which holds that spring and plunger in place. If you add disc brakes to the rear of your rig and want a quick and easy way to get a little more fluid to those rear brakes pull your metering block apart and remove the little black rubber O-ring. You can do this mod with the proportioning valve in the Jeep—just work fast and put lots of rags under the valve, as brake fluid will run out. Take too long and your whole reservoir may drain out.