07 Sierra Denali Towing Heavy Report

[ChrisNJ]

I finally got my 07 Sierra Denali w/6.2/6sp/3.42's, hooked up to one of my 2 travel trailers. I picked the lighter one, which is an approx. 7K# toy hauler. I performed this test because we need to replace my aging and troublesome 03 Burb/8.1/4sp/4:10's. Since i can not buy a new 8.1, the new Yukon XL Denali seems to be the best avail. replacement. It is only rated to 8K# towing capacity so I was worried, as our 03 burb is rated to 12K#. I know the new 2500 burbs are rated to 9700#, but have no way of testing it, however I have owned an 02-6.0/4sp/4:10's before and know what it was capable of. I will do my best to compare all of them with emphasis on the test I did yesterday.

It was 89 degrees and 50% humidity. The test was performed on I-80 from mile marker 25 to 4 in NJ and back. This road represents the typcial instersate hills and road conditions we operate in, minus a few steeper grades in PA and upstate NY.

I had trailer brakes hooked up with a prodigy and overcompensated the trailer brakes a little more than usual just incase.

I have never towed this heavy with a 1500 and was a little nervous about the suspension maybe getting pushed around, and the brakes capabiltiy, the light duty drivetrain and potential heat issues, etc... I knew the engine was more capable than my old 6.0 so was not to worried about it.

I was in tow/haul mode the entire trip. The rear of the truck squatted to about 1" from the bump stops with just a touch of front rise. I did not re-adjust the weight distributing/anti-sway setup as we tow 90% with the Burb. I put all tires at 40psi.

Leaving on some back country roads the truck performed better than I expected with good acceleration, and the brakes worked well. Average accel. put the shifts from 3K down to 2K rpm average. Felt pretty good. It felt better than the 6.0, but not as good as the 8.1 (expected). I tended to hold it's upshift point a little longer than I would like, and sometime got confused up and down some 30-50mph hills, not a big problem, just an observation. The built in engine braking in the tow/haul mode was a little too much with the engine downshifting and racing when it didn't seem to need it with the trailer brakes taking care of it's own weight.

On to the highway, I pushed her up an on ramp, about 3/4 throttle. It got to 65mph before the highway. I was pleasantly suprised. Up and down some average hills it held 65-70 with little problem. It would never go into 6th gear (good thing), staying in 5th at about 2200rpm on level ground. If you need to accel just a little it would shift to 4th going to 2900rpm and would give a small amount of acceleration. Going up some steeper grades, again trying to maintain 65, it would shift to 3rd going to 4K rpm. The interesting part here is that it could actually accel. and if you left your foot in it, it would gradually accel from 65 to 70. The 6.0 could never do this, or maybe it was the 4sp limitations. The 8.1 could but would scream too.

Trans temps got to max of 205 with 90degree heat outside on the steeper grades, and would average in the 190's the rest of the trip, even cooling to 180's cruising (no hills).

The engine braking on the hwy performed very well, not over-reving the engine, just a nice bit of help. It was also really cool to hear the 'blub-blub-blub' sound of an old muscle car decelling off the throttle with headers sound. On the biggest grade at 65 in 3rd, as i said it could accel a little, so i tried full throttle and it would accel a touch better, but the engine sounded like it didn't like over 4K rpm, while it sounded great and in it's element performing it's best between 3 and 4K rpm. Although 4K is very loud, but not needed for more than the steepest grades.

I was able to weigh the trailer at a truck stop at my turn around point and the combo was 12,700, and the trailer by itself but hooked to the truck was 5800. i will now need to weigh the truck by itself to get and accurate trailer and tongue weight. I am estimating the trailer as tested was 7K. for normal duties though I will be adding about 75 gal of water or 600#'s, and two dirtbikes or 375#. So it will see another 1000#'s, but I do not think it will matter much. Plus the Yukon XL denali will be heavier too. But it will also be much cooler ambient temps usually giving a little help. And i looked up some old notes on my larger trailer and i think it's 8K total, but will make sure later.

The engine and drivetrain did a little better than expected. It outperformed my old 6.0 setup, and performed closer to the 8.1 than I expected, although at much higher rpm's, but the fact that it did it was impressive. I almost forgot, I was very impressed with the ride. It rode much better than the 2500. The 2500 burb would be a very jarring ride with the trailers on. The denali rode better.

Tires pressures in the rear raised from 40 to 45 during the trip. the fronts only went from 40 to 42. Again the weight distributing was not set up perfect, but pretty close based on the tires temps. the tires did not feel too hot at all by touch after the hwy run. So with more weight pushed up front, i think i nailed the tire pressures.

The steering was pleasurable compared to the old burb, in much more control going by and getting passed by semi's, although a little touchy, i was able to get used to it quickly.

Result: I think the 6.2 denali set up performs well up to it's tow rating of 8K, which is not typical for a tow rating. Of course i can not predict reliabilty. The Denali passed my test.

[s-ten]

Nice write-up. Glad to hear that you found something that would decently replace the lost 8.1.

[BigJayDogg3]

I still say that the loss of the bb was a mistake and one GM will regret. The 6.0 is too weak a motor and the dmax is expensive. I guess GM has a motor in the works they don't want to tell anyone about.

[ChrisNJ]

Interesting side note: most of you know one complaint i have of this truck is it's unloaded rural road shifting performance. Well, yesterday i was driving around and low and beyold, it seems to be shifting better by staying in it's low speed gears a little longer. By it not shifting instantly down to 1200rpm, it is much more responsive. Need to put some more miles on it to tell, but maybe pushing it with the trailer on did something to the computer????