MPG with the Trailering Package?

[Wilder126]

I'm in Canada so it's in kilometres, but it seems there's an inability for the vehicle to down shift when it's needed the most. If I'm driving at 100kmph (60mph) and at a decent grade (not sure he %) the vehicle doesn't force the downshift until the vehicle until the speed reduces to 75kmph. Once it downshifts then I can really rip but as soon as I take my foot off the floor and the vehicle up shifts it has no further ability to accelerate up hill.
I called the dealership and they said it is what it is. Given your data I'm more curious about the shift points or more so the programming on when shifts occur. From what's presented, it certainly should be able to perform at least as well as the old LTZ.


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[Wilder126]

I also have a 6 speed and curious if he 8 would have been better.


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[Yukon John]

Hard to imagine the 6.2L with a 6 speed or 8 speed transmission can't do better than the 5.3L with a 4 speed transmission...The 4.10 rear is multiplied by each of the transmission ratios-meaning:

(4L60)
1st 3.059 * 4.10=12.54
2nd 1.625*4.10=6.66
3rd 1.000*4.10=4.10
4th 0.696*4.10=2.85

(6L80)
1st 4.027*3.42=13.77
2nd 2.364*3.42=8.08
3rd 1.532*3.42=5.24
4th 1.152*3.42=3.94
5th 0.852*3.42=2.91
6th 0.667*3.42=2.28

In other words, you have more torque multiplication with the 6 speed/3.42 rear than with the 4 speed & 4.10s. Effective 1st gear of the 4 speed/4.10 is 12.54 and with the 6 speed/3.42 is 13.77. Not to mention more horsepower and torque with the 6.2L over the 5.3L. Not implying that I don't believe you, but rather that there may be something wrong with your truck. There are always a few vehicle speeds where the engine is going a bit too fast to be able to downshift so there may be some of that going on but with 6 speeds that is less common as well. And this doesn't account for tire sizes, but these effects should be fairly small.

What speed & approximate grade are you unable to pass?

Josh, to add to your post:

(8L90)
1st 4.56*3.23=14.72
2nd 2.97*3.23= 9.59
3rd 2.08*3.23= 6.72
4th 1.69*3.23= 5.46
5th 1.27*3.23= 4.10
6th 1.00*3.23= 3.23
7th 0.85*3.23= 2.75
8th 0.65*3.23= 2.10

If the data available is correct, the final drive ratio for the Denali 6.2/8L90 combination should be FAR superior to the 4L60/4.10 combo. It is listed as 3.23:1.

 

[Josh61513]

With 275/55/20 tires , at 62 mph (100 kph) your motor is spinning 3,425 RPM in 3rd gear or 5,275 RPM in 2nd gear. At 3,425 RPM you have about 315 hp available, at 5,275 RPM you have about 415 hp. Big difference there. If the trans won't let you downshift to 2nd (not surprising, 5,275 RPM is moving) then I understand why grade-ability could be better at that speed. You could always set the trans to manual mode ("M") and hold it in 2nd at 55-60 mph. Or try to hold 3rd gear at about 4,000 RPM (73 mph!).

If you had the 8 speed/3.23 with same tires 62 mph would be 6,250 RPM in 2nd, 4,400 RPM in 3rd, and 3,575 in 4th. If 4,400 RPM nets about 370 hp on tap which might be enough for most grades, and if you dropped to 50 mph you could probably downshift to 2nd again (5,000 RPM) so I would say the 8 speed is a slight improvement.

For reference, your old 4L60 with 4.10 rear just held 2nd gear at 4,350 RPM at 62 mph. It never shifted into 3rd because that would be 2,675 RPM which would be gutless. That's why it seemed to grade better than your current truck. Just happens to be the ideal speed for the 4L60 in 3rd gear. Ideal speed for your 6L80 transmission is more like 50 mph at 4,300 RPM. Just a bit of an unfortunate overlap of speed.

 

[Yukon John]

When the new Ten Speed Transmission becomes available...many of these issues will be quickly resolved.

 

[pittsy]

I avg around 14mpg around town. My commute is less than 3 miles and its all stop and go. Mine is only a month old and I haven't driven more than a few miles on the highway. However, when I drive to my marina which is 6 miles away, it does jump up to 19-20 during that drive and it is in town.

 

[powerhaulic]

I am anxious to have our camper on new rig.
I will report back when that happens.....
New rig is a '17 Sierra 6.2 8spd. max tow w/3.42

 

[Broham]

What kind of difference in MPGs can one expect between the 3.42 rear end with the Trailering package versus the 3.08 without?

I will likely never tow anything heavy, but I like the lower gears for around town and I like the two speed transfer case. Am I making a mistake?

2016 Tahoe LT
Max Trailering Package
3.42 gears

Just like others are reporting: 18 mpg city and 21 mpg highway

 

[powerhaulic]

I am anxious to have our camper on new rig.
I will report back when that happens.....
New rig is a '17 Sierra 6.2 8spd. max tow w/3.42

No camper tow numbers yet
But getting 18-19 around town, 23 highway

 

[Kpwweb]

Happy to report/update I've been getting 21-22 combined. With an all-time record high of 27.2mpg over 50 miles!

Who would have thought?