My 06 in signiture had an occaisional problem when backing up with foot on the brake and not moving you would loose the assistance of the powersteering. I know others have had this and it has to do with the hydro-boost system. When driving the truck is fine. Recently it has gotten worse to where if the truck is in park no foot on the break you loose the power steering also. No fluid loss or leaks, no moans or odd sounds. It went in for the updated steering shaft, Dealer looked at in and said they ae going to put a new powersteering pump in, if that doesn't do it they will replace the gear box. My question is could it be something else, belt is fine, maybe just the hydro-boost valve?? I hate to have the truck taken apart unless I know for sure what the problem is. Thanks

same exact thing happened to me,,, was Hydro-boost valve, as you indicated..

my 01 did that. hydro boost unit as well

Thanks guys, the hydroboost valve is in the brake system not the steering pump right. I don't want to say anything to the dealer because I'm not sure, but if the problem persists after the steering pump,change I'll mention the hydoboost valve