First tow trip & some questions

[TheRook]

I just finished my first significant tow trip with my new to me 2009 Yukon. I have never towed anything before and was hoping for some insight into my experience. Yukon has 82k, HD trailering package, 1 prior owner who took care of it. I bought a Jayco 184 BS and took it for our first trip this weekend. Trailer weighs around 3700 lbs loaded with camping gear, water, etc. Have sway control, WDH, the full safety package. I went from PA to NY and back this weekend around 200 miles each way. It was hot both days of driving (around 92), heading up 476/76/287...Performed well seemingly. Some things I noticed and questions. ANY insight is greatly appreciated, I'm a complete rookie and will be taking this rig to Seattle and back this summer. Looking for any and all good advice
1) Drove 60-65 whole time, RPMs 2000-2100 normally, up steep grades went to 3-3500 max for no more than a minute or so. I drove in M5 most of the time (question on that later)
2) Coolant stayed pinned at 205-210 pretty much entire time except for a couple bigger hills where it went to 225-230 but not for long, only about a minute or 2. Then returned to 210. I felt like this was really good thing
3) All other gauges pretty much dead center. Pressure right in middle, as well as voltmeter.
4) Question: I did not use tow/haul mode at all. I only used M and set it to 5. My question is about using M. Do you shift on the fly with this? Or just it to 5 at the start? I was a little confused as to how to use it. I am used to a Subaru sportshift that is more responsive when actually hitting the button.
5) Secondary question about M mode. When climbing big hills, what is the best practice for shifting down to 4th? Do you do that prior to the hill? Or is it ok to do that while climbing and the RPMs go up? I don't want to be messing with the trans. I'm sure I have more but that's it for now. Really appreciate it!
Thanks everyone!

 

[Geotrash]

I use tow/haul mode and I let the truck decide the gear. I think you’re over-thinking it.


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[wsteele]

My towing experience with these trucks is my 2007 was 5K pound double axle enclosed trailer. I used tow mode always in “D”, that’s it.

 

[drakon543]

your well within the trucks towing capacity and there's s button for doing exactly what you were doing. as stated above your over thinking the whole towing process let the truck do what it's intended to do. manual shift mode in a car and a truck are totally different typical uses. yes it does the same thing but its not designed for the same purpose so it wont feel the same.

 

[Bill 1960]

Manual mode is not really manual gear selection, it’s just a choice of what the highest gear is. So M5 is actually just preventing use of 6. Which is a good thing.

Tow / Haul uses different shift maps to shift at higher rpm and different shift times/pressures to match a higher load. Use it.

Let the trans pick it’s own gears 1-5. There’s sometimes a case for choosing your own shift time preemptively when approaching an incline but leave that for after you have more experience and are relaxed and comfortable.

I’d want some more feedback on the cooling system performance. Sounds marginal to me but I do not have much experience towing with a 1500 GMT900. Others will know more.

An unasked question is how to control speed downhill on grades. Doesn’t matter as much on little eastern hills but on real mountain grades use plenty of engine braking (downshift) and only intermittent brief application of brakes. Too much extended braking downhill they can overheat and stop working >> major hazard. The general rule of thumb is go downhill using the same gear you use to go up it (3rd etc).

If you watch some of the TFL trucks tow testing on the Ike you can see it in action. They’ll descend with high engine revs and intermittently apply brakes to slow about 10 mph and then get off the brakes until the next brake application is needed.

 

[intheburbs]

I disagree with the responses above (not Bill's, posted while I was typing). I don't just turn on tow/haul and drive away in "D."

GM calls it "range selection mode." Whatever you set the number to, you're limiting the transmission to gears up to that number. M3 locks out 4, 5, and 6.

I agree with running in M5 when towing. This locks out 6th gear. Even if the vehicle is able to maintain speed in 6th, it's likely that the slightest grade, or even a headwind, will cause it to downshift. I prefer to reduce/eliminate those frequent shifts.

When approaching a steep grade, I typically will kick it down to get the engine in the power band prior to the grade.

I will sometimes go to M4, M3 or even M2 on long, steep grades, again to prevent frequent shifts. On long pulls, you'll sometimes hit a flat area, or even a downhill stretch, and I use M to keep it in the selected gear for when the grade resumes.

I will use the tap shift buttons (+ or -) primarily on descents, to have better control of engine braking. If your speed is too high for the selected gear, the computer will block the downshift.

I also use it in winter when driving in snowy/icy conditions, for better control. If you're stopped and put it in M2, that puts it in "low traction mode."

ETA: This was my "worst case." The "Ike Gauntlet," 7% grades, 11,000 feet elevation, 16,000-lb GCW. Trans in M2 for a stretch of about 10 miles.

 

[avalonandl]

Use the Tow Haul button. It's there for a reason.

 

[Geotrash]

To each their own, I guess. The only time I bother with manual range selection is when I know I'm going to experience a lot of upshifting/downshifting, like going over the blue ridge, and want to keep the shifting to a minimum. The rest of the time, I just let the transmission do its thing. It spends most of its time in 6th anyway, with only occasional downshifts to 5th.

I spent 25 years in Colorado and know the Ike gauntlet well. I've towed many kinds of equipment over it, and used manual mode for the uphills and downhills on both sides to keep the transmission gear hunting to a minimum.

My comments to the OP were specific to the trip he described. I know those roads also, and still believe manual range selection isn't necessary for that kind of trip. And 3700 lbs. is nothing to these trucks.

 

[TheRook]

To each their own, I guess. The only time I bother with manual range selection is when I know I'm going to experience a lot of upshifting/downshifting, like going over the blue ridge, and want to keep the shifting to a minimum. The rest of the time, I just let the transmission do its thing. It spends most of its time in 6th anyway, with only occasional downshifts to 5th.

I spent 25 years in Colorado and know the Ike gauntlet well. I've towed many kinds of equipment over it, and used manual mode for the uphills and downhills on both sides to keep the transmission gear hunting to a minimum.

My comments to the OP were specific to the trip he described. I know those roads also, and still believe manual range selection isn't necessary for that kind of trip. And 3700 lbs. is nothing to these trucks.

Thanks so much! I think people are right in the sense I was probably overthinking it. Some people were helping me out a couple of weeks ago and mentioned the M mode and perhaps I just thought that was the way. But I always thought I was overthinking it too....Perhaps on my trip to Seattle I will find it useful in some of the bigger mountain ranges out west...Since I'd never towed or driven a truck like this I was hyper sensitive to the gauges, especially since I bought the truck used. My fingers are perpetually crossed for things to go right! I was however very happy with the temps of the coolant, especially since it was so hot this weekend..Made me feel good that the engine and tranny are strong! I will be getting it serviced before I leave to do some of the other suggestions that people had....Appreciate the insight as always!

 

[gooffeyguy]

Let's not forget that if you have a 2012+ with Grade Braking, that feature isn't available when using Range Selection Mode

Also, I can't find anything in the owners manual about M2 being Low Traction Mode

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