I took the nut off my starting wheel, thinking I was going to have to pull it. I didn't. Now, my linkage is off at the shifter. Is this possible, since the wheel was never removed? How can I fix it? Thanks!

 

I have torn apart top to bottom the GMT400 truck and I have no idea what you are trying to say. Simply removing the nut from the steering wheel will have absolutely no effect on the shifter what so ever, I am really confused as to what has been done here. In fact there are seven major nuts along the steering column (from wheel to Power steering box/steering linkage), none of them could affect the shifter linkage. Could you post a picture of what you have going on?