You mentioned hydravac and hydroboost. different systems.
Hydravac uses a vacuum booster to provide power assist, hydroboost uses hydraulic pressure from the powersteering pump for power assist.
If you can bleed the brakes, and they get hard with the engine off, but has poor braking performance with engine on, you have a bad booster.
Both styles can be replaced with or without the master cyl. Probably a good idea to replace both as a unit if you are not doing the repair yourself.
When you go to order parts for that vehicle, you will need the vin number, that is the way the big truck parts are sold.
Hydravac uses a vacuum booster to provide power assist, hydroboost uses hydraulic pressure from the powersteering pump for power assist.
If you can bleed the brakes, and they get hard with the engine off, but has poor braking performance with engine on, you have a bad booster.
Both styles can be replaced with or without the master cyl. Probably a good idea to replace both as a unit if you are not doing the repair yourself.
When you go to order parts for that vehicle, you will need the vin number, that is the way the big truck parts are sold.
