I had two tires put on rear that is a little bit smaller than the ones on the front. i didnt have this problem til then. i drove about a mile soon as the tires where chnged. thats when the brakes locked down

autodr

• 260 Answers
• Posted on Nov 17, 2008

SOURCE: hurt front end

not trying to be rude but do be sure the wheel is tight. a build up of corrosion on the wheel or hub could cause the wheel not to set n lug studs correctly. that would cause a knock noise and will shake the wheel

SOURCE: 99 Jeep GC Brake Lock

todays sports utility vehicles are equiped with a proportioning valve. they are usualy located at the rear of the vehicle. this valve regulates the flow of brake fluid to the calipers. most suv`s have a ride control arm on them that is linked to the rear suspension to apply more braking force to the rear wheels in a harsh or sudden stop. if this valve is bad or malfunctioning even body roll can redirect brake fluid to the rear wheels causing them to lock up., hope this info helps

SOURCE: front brakes locking up

Sounds like the front brake hoses went bad on you. Fluid goes into the calipers and builds up pressure, and applies the brakes, because the fluid can't come back out of the calipers. Usually when hoses go, they tear on the inside, creating a one way valve type of flap. I hope that this helped. Best wishes to ya.
Bryon

SOURCE: 99 Jeep GC brake lock.

You say they replaced basicly everything that involes the rear brakes.
Every step they took to find the problem could lead to the solution,BUT did they check the inboard brakes. The brake system on a jeep that has rear rotors have inboard shoes for the parking brake.
You could have a parking brake cable that is frozen (this will cause a drag on the inboard brakes. Do you use the parking brake? Maybe the parking brake shoes are adjusted too tight?

SOURCE: 1993 jeep cherokee

It also sounds like a more likely problem is a seized caliper on the left side. If a caliper seizes, the braking system transfers the pedal pressure to the other caliper thus, the working caliper locks up. Pull both front wheels and look carefully at the wear on the pads. Both wheels should have the same amount of wear. If one side is worn more than the other, the side with the least wear is seized and needs to be changed.
Never heard of a hydraulic repostioning valve, but maybe with ABS there is one. I do know of a proportioning valve which apportions brake pressure front to back and also blocks braking to front or back in the event of brake line failure. Maybe see which he is talking about, should be able to explain the difference. Hope this helps.