I finished up the zj rear disc brake swap to my xj with a 8.25, and now I am having problems in that the rear brakes are not locking or stopping my jeep. When I push the brake pedal it goes to the floor and the fronts lock while the rear wants to keep rolling. I haven't swapped the proportioning valve yet, would this help? or what other options would help?

 

yes it would.you need the valve for disc brakes from the grand cherokee.the drum valve will not work on the disc set up.