Why won't my truck power brake?

hopwood, your wrong, i have a 98 chevy K1500 silverado with a 5.7 litre 350 to and it has plenty of power, i've done it in my truck plenty of times back when i used to do stupid stuff lol, i understand mines 5 years newer it hasn't lost as much power as a 93 but not enough to where you can power brake especially if you can do what you say it can do, and also its not the gear ratio cause im pretty sure 3.73 like mine is so thats not it either, but its got to be something in your transmission but i wouldn't recommend you power braking though, makes your rear brakes wear out faster and im pretty sure it can mess up your transmission

gear ratio and not enough power, it doesn't have enough power to spin while the brakes are on. You need a line lock to do it correctly. You are going to tear something up!

Sounds like the transmission is not selecting 1'st or (low gear) on take off, this can be rectified by having the bands adjusted. Any competent motor mechanic should be able to do that for you.
The parking brake is not vacuum assisted and it never works as well as the foot brake when the engine is running, especially when reversing this is typical of all rear drum brake vehicles. I have found that my vehicle will reverse with it's parking brake is on as well, I live in Australia and drive an Australian built 1974 Ford GT Falcon.

leak my 89 nissan wil do it

Devin, I think I know what you are talking about, but please explain to me what "Power Braking" is?