sometimes when im driving and i go to hit the brakes, the pedal feels stiff, and the vehicle does not brake. no abs codes, fluid good, no air in lines pads and shoes good

 

That sounds like a lack of boosting power from the brake booster. If you jam the pedal really hard, will it then brake? I've driven a couple trucks without power brakes, and it seems like you have no brakes until you get used to the extra effort.

 

it doesn't do it all the time. it might only do it once a day.

 

Hmm, not often, but are the circumstances similar when it does do it? That might point to something right there. Try to watch to see what 'leads up to' and 'follows' this happening. Examples: slow speed maneuvering while turning, decelerating/coasting then using brakes to slow you, hard stops and so on.

 

Mine is doing the same thing, it seems to happen when I am going slow. Its happened a few times when I was trying to park, which is not cool, luckily I haven't hit anything yet. Just the other day, I started it up, and the brake pedal was pressed getting ready to put it in reverse, to back out of my drive way, and it just started reversing out my driveway, brake pedal was pressed, but it felt hard, so I pumped it a few times to engage it better. Luckily no one was coming down the street at the same time...Otherwise I woulda hit them.
Any ideas???

 

The 97 brake boost is powered by the power steering pump. Do you have steering difficulty when the brakes are acting up? Groaning noises, hard to turn, etc. There is a screen that can be cleaned and a spring that can be stretched. Earlier models are vacuum assist, so I'd be looking at vacuum hoses and worse case, the vacuum pump.