72 brake booster
 

I think my power booster might be bad but Im not sure how to test it.My truck has a dana 60 up front with the original booster and master cylinder.My problem is I have a hard pedal and the brakes dont lock up unless its slick or you put both feet on the pedal.The pedal is harder than manual brakes but not as hard as power brakes with the motor off.

Re: 72 brake booster
 

Sounds more like a blockage somewhere. Start by using a handheld vac pump on the booster. It should suck in and hold a vacuum. If that's ok then bleed your brakes. Brake fluid absorbs moisture, then rusts and corrodes the brake lines from the inside. A piece of rust could be blocking a line. Start at the back and work to the front. Bleed the brakes until clean fluid comes out.