Just a few thoughts for you. Everything sounds good and this preventative maintenance items will give you plenty of stress relief on your trip! Working from front to back is a solid plan under the hood. 1. When you source a radiator be mi drill on non OEM units. I’ve never had issues with aftermarket and the one that’s currently on my truck is aftermarket and has seen some serious abuse in the last couple years with it installed. Only thing to be on the lookout for with the radiator replacement is to verify that if you go aftermarket make sure there’s a restrictive valve built into the top coolant hose inlet on the radiator. If that’s not present too much coolant flows into the radiator from the surge reservoir and it will prevent the truck getting up to and staying at operating temperature. Will definitely cause issues with cold weather setting in. Some aftermarket brand radiators have the redirect or valve in pace and some don’t. I purchased my radiator from 1800 radiators and it works perfectly. Several trips towing boats up and down the mountain I live on, taking my moms boat out to lake Mojave in Laughlin, Nevada where it’s 120 degrees outside in the middle of June during the day. A trip this last summer to just north of Salt Lake City and the 12 mile stretch on I-15 from mesquite Arizona, across the virgin river canyon bridge, under construction and two and a half hour traffic back up to get through, truck basically idled through that 12 miles, AC on full blast and 108 degree outside temp. Through all of it truck hasn’t had any temperature or cooling system issues. So 1800 radiators is definitely a good aftermarket brand. If OEM isn’t in the budge just be on the look out and ask about the restrictor valve. Of course OEM radiators won’t give any issues but I hear they’re big $$$.
2. Rear suspension on the Z55 equipped trucks is a common failure point beyond 100k. The air bladders around the shocks rear, leak air out, and then the compressor burns itself out trying to constantly run to keep the shocks filled. A few suitcases in the back shouldn’t cause sag so that’s a good sign of the shocks being warm and the air bladders not holding air. If the compressor doesn’t run at all that’s a good indication of it being burnt out. However easily remedy-able. You have two options. Depending on how you use the truck. Buy standard passive (non electronically dampened) non air assist shocks, resistors to fool the ride control computer, and the non air ride rear coil springs and do away with air suspension. If you don’t tow anything this is a viable option. It’s not a whole lot cheaper and from what I’ve read leaves a lot to be desired ride quality wise. But if you regulary haul people, luggage on said vacations, or tow, keeping the Z55 suspension is worth it. So you can go option two and get the replacement air assist shocks and compressor. This is the route I would recommend. It keeps the ride control the way it was designed from the factory, which is pretty damn good for a rig this size to ride as nice as it does on air assist shocks that are electronically dampened. It’s not terribly expensive, but not cheap either, but so totally worth it to go this route. Suncore is a brand that I have heard others mention here that makes replacement Z55 shocks for our trucks. It’s a cheaper option. And some guys have had good results. In my opinion the way to go is the Arnott industries brand replacement rear shocks. They are the leading brand and from what I understand remanufacture and reengineer air shacks for many different makes and models with the products for GM SUVs being the flagship shocks they offer. They offer a passive replacement option and a full OEM equivalent electronically dampened air shock setup as well. The passive versions are a tad bit cheaper. I have the passive ones on my 2006 and they ride great and have been in my truck I believe since 2018 with no issues. I got them from another member here and they were virtually new. Scored a H-E-L-L of a deal on front and rear shocks with the fronts being the OEM replacement and the rears passive Arnott shocks and couldn’t pass it up. Otherwise I would have gone with the electronically dampened version. I kinda wish I had them but I have no complaints about the performance or the ride quality of the passive shocks. Arnott does offer a compressor replacement, and Dorman makes a compressor replacement as well that’s a bit cheaper. From what I’ve read both brands can be hit or miss with failing, and everyone either swearing by one compressor or the other based on experiences. I replaced my compressor with a dorman unit and it’s been perfect since the replacement in 2018 with zero issue. There’s tons of threads here detailing the parts list, and walk throughs.
With what relaxing the shocks entails. I did the shock and compressor replacement in the driveway myself and it was pretty easy to do. I took an extra step and replaced the air lines going from the compressor to each shock just to be safe. Wasn’t necessary but I figured hey I’m in there may as well knock it out for extra peace of mind.
@Joseph Garcia has great experience with the Z55 systems on these things as I believe he recently rebuilt the system on his 2007 Denali XL. He can correct me me if I’m wrong, but I think his truck had the Z55 delete done before he bought and he went back to the Z55 setup.