I have a TH400 with a TCI reverse v-body,is your full manual?I think all t-brakes are ,but not sure??Mine,I had to take the brake band out of the tranny.I think it is a sorta safety feature for shutting down,not sure.But,mine has NO engine braking,except high gear.When you let off the gas it seams like it just free wheels.It's just where it returns to idle,instead of holding back.Maybe this is what you are feeling???