well put on the napa rear wheel cylinder for a chevy for better braking. ithink it was 37337? anyway i surely didnt notice any difference in braking. i think i just waste my money and time.any help?

 

what yr is your truck, your sig line is not filled out, hard to help without info...
so I'll try.

have you adjusted your rears properly? sounds like a simple question, but believe it or not even mechanics cant do it properly.
so here is the test, hop in the truck, apply the brakes, note pedal height from the floor, pump the brakes once and note pedal height again, pump the brakes once more. if the pedal seems to rise, its a dead give away your brakes are NOT adjusted properly, and they will need to be done again.
rear prop valve rod can be lengthened as well to apply more pressure to rear shoes