The Zip

I think riding on smooth surfaces and dips with 20s or 22s should be similar regardless of the suspension, it will probably be a smoother ride if the 22's are wider. The difference will be when you hit a pothole or bump with more rubber (20) vs more wheel (22).

Type of suspension was/is based on specific truck package not tire size. Example; Tahoe LT came with Premium Ride suspension whereas the LTZ came with Magnetic Ride suspension, both could have 20 or 22's.

Don't look past a bad alternator. Back in the day surging was happening to me and I rebuilt the alternator, surging gone. Take it to a auto parts shop like Pep Boys and get an electrical diagnosis.

When/if you contact the dealer ask them first thing do they repair many shocks in the fullsize SUV. If they say no, then it is a good chance vibration caused your shocks to go bad. I don't recall reading on this forum GM repairing shocks for a vibration, but if you know GM has been repairing shocks when owners make some noise then make some noise. Don't know if you can be too loud though, your truck is probably out of warranty like mine. You seem to have a pretty good relationship with the dealer and the vibration is on record, they may be receptive to covering parts and labor or either.

Unfortunately, 2015 + Denali + XL = vibration problems. Vibration problems are not as talked about today which could mean GM fixed the issue or folks just don't want to bring it up. Don't know if your shocks are related to the vibration, but it would make sense to me that uneven tire wear added with leaking shocks "could" be a result of a vibration.

I can understand maybe feeling helpless if it was out of warranty, but if you have some more time on the warranty, take it in to the shop. As much as we want our vehicle to be perfect, car building and repairing is not a science. If it were, it wouldn't be warranties. Electrical issues and molding may not happen, but after you allow the warranty to work and it ends up with electrical issues and mold then time to let it go.

Owners of 15-16s voiced their opinion of a problem, owners of 17-19 tolerate the problem. So I somewhat agree with this comment cause I don't read as much about problems. The Chevy Shake was more with the pickups vs the fullsize SUVs. The SUV big problem was buffeting and pressure.

You covered all the bases. If it is the wheel, a little time refilling with air twice a month will save a little money on a new wheel. Don't think you can seal a wheel without coating again?

Could be losing air through the valve stems. Pick up a $2.00 tool and tighten them up and see if that made a difference.

Did you see sales for the Gen 4 GM Fullsize SUVs for 2014 and 2015? To "strongly advise to avoid 2015s" suggest there has to be a ton of complaints for that year from different owners. Problems with the first year is still happening, folks are just tolerating it because of the functionality and look of the GM product. Jrny4rbys sound like he's done his homework, I would recommend just be cautious of any first year issue. If he was basing his purchase on my 2015, he would have been in his truck yesterday.

Don’t think you'll see many of these trucks driving hard, they’re too cushy and costly to do anything more than towing or hauling. Some would argue all the trucks have the issues mentioned in your OP, but then a majority of folks without problems are not posting. 1) Buffeting, either you have it or you don’t. This is not model specific, but in the early years most of the complaints were from GMC owners (Denali XL with 22” wheels), followed by Chevy and then Cadillac. 2) AFM, I don’t recall any of the issues you mentioned. I have a first year Gen 4 truck and it transitions from 8 to 4 and back seamlessly, only notice it if I happen to be looking down as the change occurs. 3) You got it right, just look under the truck to see what you can. This is going to be location dependent where the truck spent most of it’s time. I’m out west, no snow, rain, ice, salt. My truck just went over 5 yrs, no rust. If a touring sedan could tow and haul like these trucks, that would be the only thing I would compare it to. But then again, the new Maybach SUV going for 200K could be the best of both worlds. The engineering in the GM fullsize SUVs is more car than truck like though. If you end up getting one of these trucks (without any issues), you’ll see what I mean.

If you don't frequent soft sand/mud/snow/or ice, then a RWD with all weather tires is fine.

Be careful when asking an owner for advice, one like me will tell you my first edition truck is the best thing since sliced bread, the internet, or a microwave oven (bar is set low). But another owner may tell you his truck was the biggest POS he ever owned. I have not read as many issues with the later editions, but the problem areas were buffeting, pressure, shaking, and vibration. So read some of the earlier posts before making a 50K+ investment...

Had this problem a few years back, advise the service tech to replace the AC High Temp Sensor (titled per my invoice). Mine was done in 2014, problem never came back. I'm talking Chevy, should work for GMC.

This comment is accurate since the 2015 first issue, but reported SUV numbers on this forum has decrease from the first issue to now. I have a 2015 first issue, never had the shaking, or RFBd tires, or buffeting. I was one of those other vehicle specifics.