2000 F150 4x4 4W anti-lock disc brake. Rear brakes hang up only in reverse. E-brake is free and so are caliper pistons. Rotors and pads new last year.

 

both sides lock up?? if so....disregard my following thoughts...

I believe that year has e-brakes with shoes inside drums on rear....Have you checked your E-brake shoe retaining springs? perhaps trailing edge of e-brake shoe is loose and therefore hangs in reverse....e-brake could still work correctly in that scenario....

any noise at all when you roll wheels? any abnormal brake dust?

 

I checked emergency shoes and lubed fulcrums when I replaced rotors and pads last year and springs were ok, but might be a good idea to check for broken retaining spring. I always hate trying to get rear rotors off, even after only year old as you get that rust ridge on inner lip.

Thanks for the idea and will pull apart when weather gets better. If they look good I might just replace both calipers as truck isn't driven much, but every time I can push pistons back which gives me doubt. You'd think if calipers pistons were sticking I would get overheat and drag when driving but don't.

Thanks