I have a 2004 Sierra Denali awd/4ws and I am having two problems. The first is that I am getting a thud felt through the steering wheel almost as if someone was banging on the steering column. I feel it mostly in turns but it is noticeable all the time. Secondly I have been getting what I can only describe as a vibration like when you drive over rumble strips in the road. I only get the vibration while I am driving and get into fourth gear. What will happen is that it gets into fourth gear around 40 mph and I let off the gas to coast for a while and then when I get back on the gas it makes this rumbling vibration. It only happens when I am off the gas and coasting around 1000-1200 rpms and than I lightly reapply the gas. If I get on the gas it seems fine. It is almost like a stick car when you are in too high of a gear. Any clues?

For the rear end rumbling get your rear end flushed and make sure they install new Quadrasteer specific fluid in it. Second, you may need your intermediate steering column replaced. There is a Technical Service Bulliton (TSB) on this item. If your truck is still under warranty it will be covered, if it is still not under warranty it'll be a judgement call for the dealer.

Good luck and welcome to the Club!

It is still under warranty so I guess that is good. I will get the rear end flushed and will definitely make sure they use the lube for quads. Thanks for the information.