Q: rear brake locks up on 2003 Ford Windstar

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
why is my rear drivers side brake locking up. New brakes, made sure no air in line and the abs light is not on. Let up off peddle they release ok but when u put just a little pressure on it the brake locks up while driveing on gravel or snow dont notice it driveing on paved roads.
(1) Answer
(2) Comments
could be adjusted too tight, emergency brake cable may be seized and not allowing the shoes to seat correctly or the drum is out of round and needs to be resurfaced.

I dont think its the emergency brake. I checked it and it seems to be working fine. Could it really be the drum? It is old and rusty replaced every thing but them.