sounds like load sensing valve needs adjusting-i take it shoes ,cylinders and linkage in drums have been checked/cleaned/repaired and adjusted as neccessary. whilst watching l.s.v. get someone to press foot brake and you should see arm move slightly [to confirm it is working] then refering to label on n/s/f door for setting-basically if you slide spring lock bolt up and pull spring down this will decrease braking to rear brakes . effectively shortening spring,.
k, July 2008