I don't think you need a proportioning valve with disc and drum setup from what I have read on the parts people websites. My pedal travel is minimal. On Monday I am going to call CPP and see if a dual diaphragm booster would be better. The truck weighs 4,000 lbs you know. Maybe I am expecting to much but I don't think so. I believe with the old shoe set-up, up front when we moved pulling two motorcycles the brakes were better. I have a good pedal no matter when I hit it. And I may hit it with a sledge hammer soon.
Thanks Sharon
