Hi all, in my 95 RWD pickup, I have twice recently felt my truck slowing down significantly and pulling to the right as though a brake was engaging. In both instances, I had not touched the brakes for probably at least a couple miles and had accelerated somewhat hard uphill. Also both times I parked for a couple minutes and then tried to go again and everything seemed fine. I'm not really sure where to start looking on this and hoping for some direction.

 

Jack it up and see if you can detect any slop or any difference in turning resistance between the different wheels.

 

If you have a brake dragging it can get hotter and hotter and drag more and more until it cools down again.
the only other scenario I can come up with is heat generated under the hood increasing pressure in the brake lines and whichever brake is working best starts to drag. this could only happen if the brake pedal or master cylinder pushrod are mis-adjusted or there is a blockage in the brake lines somewhere.
Go with millball's recommendation and see if there is an obvious difference in rolling resistance, also when it is hot and pulling figure out which wheel is dragging, front or rear can make a big difference when it comes to diagnostics here.