Ahoy!

I believe my brake booster is dying! It's coughing up blood and keeps confessing to committing crimes that were committed before it's time!

Here are my thoughts and along with them come questions that maybe someone on here can help me with. My 75 F150 had power brakes. My 77 F100 had manual brakes. I swapped everything from the master cylinder back to the pedal assembly from the 75 F150 over to my 77 F100 and converted the it to power brakes. They work AH-mazing, granted, everything else has been replaced (calipers, rotors, pads, lines, drums, shoes, hardware), but it stops better than my wife's '03 Accord.

My 78 Bronco has power brakes. I've looked into the common upgrades that people do/recommend, such as the F350 dual diaphragm booster. I really like the braking action of my F100 and, although it's definitely lighter than my Bronco, I think it'd stop the Bronco on a dime (or at least a nickel) if I can get a similar setup. I know there's a write up that gives a whole rundown where you swap out a single for a dual diaphragm, change from single to dual piston calipers, bigger wheel cylinders, on and on. I don't really want to go that far if I don't have to. A '78 F350 booster has two 9.25" diaphragms. My '78 Bronco has one 10.75" diaphragm. My '77 F100 now has one 11.50" diaphragm that came from the '75 F150.

I guess my question is will .75" make a significant difference on the single diaphragm performance? I know going from an old, wheezing diaphragm to a new one will make a difference on it's own, but I'm assuming an extra three quarters of an inch will make a difference. That's what she said. I'd be putting on a new master cylinder as well. I think keeping the pressure higher with the 1" bore rather than going to the 1 1/16" bore master with the dual diaphragm would work better if I don't upgrade to dual piston calipers. My F100 requires very little effort to stop it under normal conditions, it's a matter of resting my foot against the brake pedal, which is very nice. I know the overall diameter of the booster I have on my F100 is larger than the Bronco, but it should still clear everything if I get another one like the one the F100 has. I don't know if the studs on the booster that mount onto the bracket between the booster and the firewall have the same spacing, I'll look into that. The back of the Bronco booster is tapered and longer vs not being tapered on the other booster. I also don't know if having a '78 Bronco pedal assembly combined with a '75 brake booster will cause any issues. I'll just have to verify the length of the push rod coming out to connect to the pedal linkage to make sure they're the same length. I don't need my pedal starting an inch from the floor or anything! Just some stuff I'm mulling over.

'78 Bronco Booster.

'75 F150 Booster.



Also some videos I'm watching for great success!