I have a 2006 Silverado 1500 (5. 3L Z71 ext cab, 40K miles). For the past several months, I have noticed a popping noise coming from under the floor board on the driver side when the vehicle enters a slow turn. It has been gradually getting worse. I have read numerous posts about the intermediate steering shaft issue, but after reading the TSB for this problem, I don't believe this is the issue that I am having. My brother's 3/4 ton Duramax has the steering shaft issue, and he says it makes multiple "clunks" when he is turning, and he can feel it through the steering wheel. In my case, there is only one, single, definitive "clunk" while I am turning. It only does it at moderate speeds (10-20mph), and during both left and right hand turns, but it doesn't do it all the time and is sometimes hard to recreate. I also do not feel the thump through the steering wheel, but I seem to be able to feel it through the floor board. In the I-shaft TSB, it mentions that some people can hear a noise, but not feel it in the steering wheel, and they should refer to TSB 03-08-61-002F (Remove front crossmember, change fastener orientation). However, I can't find a detailed version of this TSB online, and I can't find anyone else who seems to have this issue. I would assume that the crossmember that the TSB is talking about is the one near the transfer case, but the noise seems to come more from the front of the vehicle. Also, the only version of this TSB that I was able to find just mentioned cleaning off the undercoating on the crossmember and reinstalling it. But since the title says "change fastener orientation", I would assume that there would be more to it that just cleaning off undercoating. Any advice? Am I on the right track? Thanks for your help. . . I am new to this site, but it looks like it will prove to be very helpful.