Right rear brake locks up

Try opening up the bleeder valve on that brake, does that cause teh brake to release? Is it locking up and binding or is it not releasing? Or both? Does it lock up and squeel when u try to slow down to stop?

Have you ever had teh ABS system checked?

Is it a diagonal split brake system or dual split. Ie left front and right rear and left rear and right front?

Brake line could be plugged, you have a 4 wheel antilock or front wheel antilock and rear wheel antilock?

Take and disconnect your abs speed sensors and try to drive it. Does it stop better now? You could have a bad wheel cylinder, it may not be releasing fully and over a few stops th epressure builds up enough to cause them to self apply and grab when you brake.

Try new brake adjuster, springs, etc and a caliper.

You should be starting a new question for your vehicle. Unlike other sites where anyone can add a comment, this was a private conversation between two people. For the rest of us, it is listed as having received a reply, so we don't get to see your addition or have a chance to reply. That won't get you the help you need. I only stopped in to see the results.

In this case I suspect a common issue was overlooked. Almost all pickup trucks and minivans can have a wide range of loading in the rear, from empty to fully-loaded. As such, more braking power is needed in the rear when carrying a big load, but that would cause easy rear-wheel lock-up when lightly-loaded. To address that, they use a height-sensing proportioning valve in the rear, with a linkage between the body and the rear axle housing.

With age, the vehicle's springs sag and ride height is reduced. That is checked by alignment specialists, and must be corrected for best handling, tire wear, steering response, and comfort, before performing an alignment. Ride height also affects front-to-rear brake system performance, but in this case, sagged springs make it look like there's a heavy load in the rear. More brake fluid pressure goes to the rear brakes than is needed, thus the easy rear-wheel-lock-up.

On Chrysler minivans that height-sensing proportioning valve is easily adjusted in less than 15 seconds. For other brands, some have an adjustable link, or there may be some other means of adjustment. If there is no way to adjust that valve, the only fix is to replace the springs to restore proper ride height. Every tire and alignment shop has small books showing every vehicle, where to take the height measurements, and what they should be.