Had a problem going down road, brakes applied all by them selves, their was no give in break pedal, had to pull over, turned off, let sit for a half hour or so while trying to figure out what was going on, didn't find anything except hot hubs, started back up everything is good again, suspect the cruise control. I was messing with it earlier in the drive, about 20 min before it happen, pressed a few buttons, it does not work, anyone know how to test. I know don't press any more buttons, LOL!
Repost, previously posted under wrong forum.

 

Have you jacked it up & checked for a brake that's adjusted too tight? Might be dragging & overheating the fluid.

When my cruise control was'nt working I pulled the trouble codes & BINGO I got a code 29 "vehicle speed sensor voltage is too low." 30 bucks for a new sensor & problem solved. Take a couple minutes to pull the codes.

 

Did not get any codes.

 

And in the FWIW category 1988 was the 1st year that Rangers had a CEL (check engine light) on the dash. Your 87 does'nt have one. So on an 87 the only way to know if theres a trouble code is to hook up a scanner & check.

 

Had codes checked. none. But I did find. Remove the Master cylinder and checked Booster push rod, way to long, 1.35, adjusted in to 1.0, any longer and I would have to draw in master cylinder to mate surfaces. 1.0 seams to be the perfect length to wear the Master cylinder mates up with Booster with no effort, pedal and brakes are fine now, problem fixed. Thanks for advice!

 

Thanks for the update and congrats on finding the problem.