2015 Yukon Denali 4wd production June 2014 75k miles.I have been reading this topic from the first day and I can see there are multiple fixes that didn't solve the issue but improves.so I decided to do what I think it improves the ride quality to this $70+ suv. First I replaced all of shocks no more mag and no more air at the back,I went with bilstien 4600 series and I think I need the 5100 series for offroad use,the dealer install resistors to stay away from dash messages,second I went with 17" methods wheels and Yokohama,third I had a custom catback done by local shop,forth I tuned the car by Justin at blackbear tuning he disable the v4/v8 mode it's v8 all the way.with all if those modifications the car is much much better than before,today I took the car to dealer for oil change and spoke with chif engineer and he told there is a new updated steering bushing that will eliminate the vibration that occurs at 70 miles speed.he also told that new Yukon came with steel control arms the first productions were aluminium,also GM updated the engine mounts with hydraulic type.i asked him to replace the steering bushing with the updated one and see.overall the changes I done was mandatory as I use this car on off-road and I can say I really improve the ride.