[quest]

Do you mean hydro-boost or vacuum power booster, what year is this truck? Do your wheel cylinders look good when role back the rubber and peek inside, should be nice and clean with no corrosion and the rubber should not be dry or cracked and should easily be able to slide the pistons back and forth in the cylinders?

If your rear diff bearings are toast as well keep in mind that you will need to completely drain all the gear oil from the diff and put in a fresh load in with the new bearings. I like to preload the rear bearings with a little bearing grease when I reassemble it to be sure they are not starved of lubrication when they turn under load for the first time. After that the gear oil will do the job.

I have a 65 3/4 ton 4x4 with manual brakes, a full line of replacement parts was going to run me about $750 a couple of years ago, including drums and brake cables.