Here is my list….
1) Water pump gasket leaks. Most often misdiagnosed as a $300 leaking water pump rather than $10 gaskets.
2) Engine mount failures. The Pre-2006 trucks as susceptible to the rubber portion of the engine mount to get over heated by the exhaust manifold and the rubber collapses or crumble then fall out. GM has a new engine mount with a heat shield to protect against the heat from the exhaust manifold. The new part number is 25828247. Both LH and RH mounts are the same part number.
Failed original mount on left and new design on right.
3) Steering column clunk from the upper intermediate shaft. The original GM bulletin advised to pack it with grease. That was a short time fix that didn’t last very long. GM has had a new design upper intermediate shaft available since early 2008. Part number 19153614
4) The electric shift 4wd system sucks period and is the most unreliable system on the entire truck. Control head failures are the most common failure but the encoder motor on the side of the transfercase is also susceptible to salt water intrusion, which will eventually lead to a failure. The transfer case control module doesn’t have the best track record in reliability either. The AutoTrac transfercase in the non-HD trucks also has a habit of burning clutches. These issues and components are all common with Dodge trucks as well being all this crap is from the same suppliers.
I worked at the GM Technical Assistance in Troy, MI then later Pontiac, MI during the beginning of my automotive industry career before moving to the field. The rotation group I was in received at the time (1998) received call after call on electric shift issues on all GM trucks across the board. The S-series trucks and blazers were the worst! I went out of my way to purchase a manual shift transfercase on my ’98 Z71 and later my ’01 HD. I had no choice on the Hoe as NP8 (AutoCrap) is standard. My new used 2005 HD also has a manual shift tcase.