OE style brake booster

[Nick_R_23]

So I’ve noticed that the chain auto parts stores still sell the OE style brake booster. Do these bolt right up to a truck that had manual brakes stock, or are modifications/additional parts required?

https://www.oreillyauto.com/detail/c...+booster&pos=2

[ray_mcavoy]

No, they're not a direct bolt-up. Additional parts are needed to mount one on a truck that originally had manual brakes.

There is an adapter plate that bolts onto the firewall using a couple existing holes (I think one hole has to be drilled). In addition to adapting between the different bolt patterns, the wedge shape of the adapter plate angles the whole booster/master cylinder assembly off toward the driver side fender (I believe that's done to clear the air cleaner on inline-6 engines).

There is also a bellcrank assembly that goes in between the mounting brackets on the booster and serves to connect the pushrod on the back of the booster to the pushrod going to the brake pedal. I believe the purpose of the bellcrank assembly is to change the overall pedal ratio, keeping the power brake setup from feeling "over-boosted" while still using the same pushrod hole in the brake pedal.