Steering Box For 03 Tahoe Question

[tx tahoe z71]

So it looks like my steering box is worn out as my steering input isn't reflected on the steering box output (my friend turns the wheel, but the pitman arm doesn't move much).

 

I called up the dealership to get the p/n, 88965542, for a 2003 Tahoe Z71 4wd. I asked if the 2wd p/n was the same, he said no, 26110836 for 2wd. I would like to go to a junk yard and pick one up and don't want to have to find a 4wd truck to get one.

 

He speculated the difference was due to the steering ratio. Can anyone elaborate on this or confirm this? Which ratio is higher (I imagine 2wd but don't know for sure)?

[tx tahoe z71]

Anyone anyone?