This happened a few years back. With no warning at all stepped on the brake to stop and pedal went straight to the floor and steering locked up solid. It was a Tee intersection and truck ended up in someones front yard. I had quickly slammed my foot down on the parking brake to stop. Normal operation after that. It happened again about a week later. This time I let off the brake and I got the steering back and rolled thru the stop sign and made the right turn as no one was coming. This is a joy to experience! Found nothing online about other trucks that are brake boosted. Had the power steering pump replaced at a independent shop in town and it'* been fine ever since. I can't be the only one in this country to have this happen! contacted Chevy and they never heard of this happening! This should be considered a safety issue.Every 2500 owner please be ready when this happens to you.

Yeiks that is a scary / dangerous situation to say the least. Did the truck stall then went to floor, or was it it still running?
Good thing the parking brake was in working condition.Good to know after the PS pump was replaced it was ok after that.
Power steering fluid works hard & it is a good idea once a year to at least suction out the fluid & replace it. Flushing though is the best.
Same with brake fluid, if you are not bleeding the brake fluid every year or 2 consider replacing the brake fluid as it is hydroponic.(likes to absorb moisture.)

Yeah this is something that happens with hydroboost when the pump gets worn out and/or when the hydroboost unit starts leaking inside. I'm guessing you have probably a couple hundred thousand miles on it. There is a weep hole on the bottom of the hydroboost facing the master cylinder. If it isn't dry then something needs to be repaired or replaced, usually the hydroboost unit.

My advice: Beware that a similar thing happens when the accumulator in the hydroboost goes bad. It will let the brake pedal bypass and go to the floor, feeling like a minor spring is pushing back against your foot. It'* will likely still be braking a little, but not much. Release all the way and try again less hard and it should work better. If the hydroboost is old it'* worth replacing just for good measure.

110k on truck when happened. Nothing in pedal. Nothing coming from hydro boost unit. Fluid changed twice @ 50k intervals. Not 1 ounce of warning before complete loss of pedal!

Wow!

Well for what it'* worth: This doesn't happen often that I know of.