Help! Suburban won't turn!

I have a 00 Suburban 1500 4wd and when I move the steering wheel the tires do not turn. I looked and a nut is missing from one of the pieces! Not sure what it is called! Does anyone know what piece I'm talking about?

Wow...a nut is missing...from under the dash? or the front of the truck? Possible broken pitman arm if its on the drivers side, or idler arm if on the passenger side. A pic would be helpful.

I have a 00 Suburban 1500 4wd and when I move the steering wheel the tires do not turn. I looked and a nut is missing from one of the pieces! Not sure what it is called! Does anyone know what piece I'm talking about?
the steering box is under the pump. the nut is used to put a pre load on the gears. how long you have this vehicle ?

the hard steering is common problem when with high miles and hard use as the steering box gear wear.