1990 Ford Ranger Rear Brakes lock up when applied hard

First thing comes to mind is leaking rear axle seals.... expecially if you live in colder temps...

From what you've written the only thing left is the brake hose. When they collapse internally there is nowhere for the fluid to easily bleed back.

Bill

You would think that if the hose collapsed, both rear brakes would be affected. I've seen this to not always be true. If the brakes are misadjusted, the tighter brake will "lock" when the looser one will release. It should equalize, but it doesn't always. I don't claim to know why, just that I have seen it. The chassis to axle hose had collapsed internally causing just this symptom.

If the E-brake cable is siezed, the brake shoes wont be properly positioned on the anchor pin when released.... This can affect brake action. Contamination of the brake shoes.... Are the shoes properly situated? That is to say that prinary and secondary shoes haven't been put in the wrong spot inadvertently....Hoe about the backing plates? Are they deeply scored on the pads where the edge of the shoe rests?

Most of these types of concerns result from inattention to detail or lapses in sanity...

Ask me.... I can tell you...