towing experience with a 2017 denali
So, I've towed before, I had a Saturn ion with a very capable hitch and manual transmission. It actually towed my 6x12 trailer very well, even on the highway at 3500LBS combined trailer/load weight. The engine (some bolt ons and a tune) the OEM brakes, open differential, and stock mirrors, all did very well and instilled enough confidence to safely tow it across the hilliest parts of Wisconsin and the upper peninsula of Michigan. the only thing was tongue weight had to be carefully managed and being fwd traction on gravel hills was just barely enough to start from a stop.
I was all excited to try the acadia, because I figured it was built to tow. I was sort of right and sort of wrong. Total vehicle length is within a foot of the Saturn, GCVW is within 100LBS, and I'm up about 110HP, but aerodynamics is not the .31 (not stock) of the Saturn and relatively low drag of a utility trailer. so, it's closer than you think.
the trailer is a starcraft 12 foot pop up camper, and I have no delusions about it, the Saturn could not handle the tongue weight safely with that hitch and sock suspension. The acadia barely even squatted with the tongue weight around 300LBS, did fine around town for power, brakes were great (trailer also has a brake), but I'm glad I didn't get anything bigger, which they tried getting me to do. The mirrors are terrible compared to the Saturn, and fwd grip couldn't maintain momentum on a gravel hill, much less start from a stop. Hill hold is really nice, and once I engaged AWD, it went up the hill without any wheel spin. Anyway, on the highway it seemed to struggle more than the Saturn, so I'm guessing aero is to blame for this, and the mirrors gave me no vision of behind the trailer unlike the Saturn's, I had to turn around and get tow mirrors. The transmission was around 180 on the hills, which I'm not a fan of, but it doesn't seem excessively high. A trailer sway management system like ford has would be appreciated, but it didn't sway too easily. I got 24MPG on hilly terrain at 50MPH, which isn't bad. I would imagine with a utility trailer it would be fine to do the 4000LBS, but I wouldn't do it with anything bigger than a popup trailer unless you put some serious effort into aero.