I've had something very similar with my 02 Tahoe. Read my thread about the symptoms and see if it is the same. https://chevroletforum.com/m_46045/m..._/tm.htm#46045 They've come out with a brand new part that replaces the old Int. Steering Shaft for the Tahoe atleast. That GM part number is: 19153614. I'm going to try and get the dealership that installed the first replacement shaft back in 04 to replace it again with the new part. Wish me luck because I'm sure I'll need it.

I'm not a mechanic, so I can't do the self-fix. I'll probably pass this lube fix along to my mechanic though.
Good luck!

 

Well, I fixed this problem today. All I did was disconnect the steering shaft at the steering gear, (which consisted of removing one bolt) and then I moved the shaft in and out of the firewall about half a dozen times and hooked it back up. Problem solved, no more clunking. Apparently moving the shaft around sucked the existing grease back on the splines. So it cost me absolutely nothing, and took about 5 minutes to do.