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jgerardi · 07-16-2013, 07:49 PM

I pull my 23 ft international with a 2013 Avalanche. What is the best way to take on a hill? Should I try to maintain a constant speed and allow the truck to down shift and the revs to climb? Or is it better to maintain constant rpm?

dwightdi · 07-16-2013, 08:25 PM

For the best gas mileage, I would start at the legal speed limit and keep the throttle the same while allowing the truck to slow down and downshift when necessary. I use the tow haul mode when in the mountains. I also use tow haul on the downhill runs to allow the engine to do some of the braking.

HowieE · 07-16-2013, 09:16 PM

Each engine has it's own sweet spot on the power curve. Your best choice would be to select that engine speed that maintainss that rpm while climbing the hill.

Lugging the engine by holding a higher gear will result in higher heat build up of the coolant and exhaust temperature.

Over reving in a lower gear has no advantage.

Trial and error you will eventually find that spot if you can not find someone that can tell you it for your engine.

As important as climbing a hill is descending it. ALWAYS use the same gear going down as you used going up. Sound funny but your will accept this if you live through a runaway and lose your brakes.

ROBERTSUNRUS · 07-16-2013, 09:36 PM

Hi, this depends on a lot of things, but for me, I hold the speed limit, take it out of overdrive just before the climb, and manually drop it into second gear [4 speed] holding it at about 4,000 RPM at about 60 MPH.

DryFly · 07-16-2013, 10:04 PM

You have a modern TV with state of the art (close anyway) computer controlled transmission - why not use it? Stick it in "drive" and go the speed you want. If you want to save gas then slow down. Manually shifting a modern transmission is gratifying only if you think you're better at shifting than the computer system in your TV -"(you're not). You don't own a manual transmission, you own an automatic.

cwf · 07-16-2013, 10:06 PM

Screaming in my best war voice..... Nah

DryFly · 07-16-2013, 10:13 PM

You're TV has a modern high tech state of the art ( well, sort of ) automatic transmission - why would you think that you are smarter about transmission/engine/weight/fuel/traction management than it is? Put it in drive and go the speed you are comfortable with!

DryFly · 07-16-2013, 10:15 PM

Sorry for the double post, I'm out of town using my iPhone, and it's smarter than I am

jgerardi · 07-16-2013, 10:29 PM

Thanks Dryfly
The advice is so good I enjoyed it both times!

withidl · 07-17-2013, 12:19 AM

I try to keep my TV transmission in torque converter "lock-up", i.e. in direct mechanical drive as this is more fuel efficient and generates less transmission fluid heat.

In "manual" mode it will stay in "lock-up" as long as my indicated speed doesn't drop below 60 mph, so to maintain at least 60 mph, as I see a grade approaching I will override the cruise control and throttle up 5 to 10 mph so that the TV will not drop below 60 mph before cresting the grade.

If the grade degree and duration are such that a lower gear is required I will manually down shift so as to stay in "lock-up" in the lower gear.

I generally set the cruise control at ~64 mph which is about 2,200 rpm in 5th gear with "lock-up". The gas engine is 4.4 liters and makes ~300 hp and ~350 #/' of torque; the Airstream is 31' with a GVWR of 8,300#.

JFScheck · 07-17-2013, 04:45 PM

Uh - some interesting posts here....

I would throw my hat into the ring - if your TV has been made within the last 8 years and comes with its "brand" of tow package, put it into Tow Mode (assuming it has one) and drive it up the hill at a speed you are comfortable at an RPM level that keeps you within your powerband (you can tell when you accelerate

JimGolden · 07-17-2013, 05:04 PM

Dad used to drive big rigs when I was a kid. He always said to pick up some speed before you hit the bottom of the hill. So if it's a steep one, I try to pick up 10-15mph additional if it's clear and no gendarmes around. Of course, if it's a really long hill, that doesn't help you that much (like that one on 77 going from NC back into VA that is about 7 miles long and very steep).

I do have a tow/haul mode so I just switch into that. I'm running a diesel though, so your experience may vary...

Like the others said: Don't lug it, and don't spin the wee out of it. Just get it to a comfortable speed/rpm and cruise on up.

cwf · 07-17-2013, 05:04 PM

"Drive it like you stole it!"

That is common theme from a MC forum... And the machines, being German in origin, tend to smile back at ya!

VTSafari · 07-17-2013, 05:23 PM

Sometimes you are smarter than the automatic transmission deciding when to shift. You have eyes and can see what is coming. When coming up the hill to my driveway...which is dirt I start manually shifting and put it is 4 wheel drive. Before I turn into my driveway I am in first gear. Leading up to the driveway and going up the driveway the hood of the truck is higher than the roof of the back end of the airstream. I have tried tow/haul mode....the transmission prefers me shifting. Having said that on the open roads I do use tow/haul mode when areas with hills. Maybe a bit of speed increase coming to a hill and definitely don't try to make it up on the downhill. Lot's more accidents going downhill than up.

Bill

perryg114 · 07-17-2013, 05:36 PM

He is right. You want to keep that torque converter locked up and the best way to tell is to get something like a scanguage II that monitors things like transmission temp, slip ratio (1.0 is locked) etc. Computers are only as smart as people make them. Transmissions overheat real easy if the torque converter is not locked. If the temps start rising too fast then downshift. If that does not work take your foot out of it. If that does not work slow down and pull over with the motor running till the temps come down. If the transmission is hunting for the right gear lock it into the lower gear.

Perry

Quote:

Originally Posted by withidl

I try to keep my TV transmission in torque converter "lock-up", i.e. in direct mechanical drive as this is more fuel efficient and generates less transmission fluid heat.

In "manual" mode it will stay in "lock-up" as long as my indicated speed doesn't drop below 60 mph, so to maintain at least 60 mph, as I see a grade approaching I will override the cruise control and throttle up 5 to 10 mph so that the TV will not drop below 60 mph before cresting the grade.

If the grade degree and duration are such that a lower gear is required I will manually down shift so as to stay in "lock-up" in the lower gear.

I generally set the cruise control at ~64 mph which is about 2,200 rpm in 5th gear with "lock-up". The gas engine is 4.4 liters and makes ~300 hp and ~350 #/' of torque; the Airstream is 31' with a GVWR of 8,300#.

JFScheck · 07-19-2013, 03:22 PM

Peeps - my humble opinon, if you have to go through all that to tow in the mountains then you have either too much trailer or not enough of a tow vehicle....

Silver Hawk · 07-19-2013, 04:24 PM

I aree with "JFScheck" above: - Get a Cummings and don't worry about it!

Steamguy · 07-19-2013, 05:26 PM

One thing I haven't seen mentioned... something I learned from our old Master Mechanics: the engine itself will tell you what it's happiest in doing. Some like to rev up and just pull, others like to take it a bit easier. One of the biggest telltales is your oil consumption. If your oil consumption suddenly goes way up, then you're being too hard on the vehicle.

For my experience with an SOB and my particular tow vehicle, it's happiest if I let the Tow Mode and the automatic transmission do the work; I just go to Manual Mode if the transmission is 'hunting' for a gear. I allow my speed to drop by 5-10 MPH on the long hills; that's what the right lane is for.

The proof for me is going from using 1-1/2 quart between changes to none. Gas mileage has gone from a little better than 8 to a solid 10+ MPG. And where I live, you can't get anywhere without going over long hills...

perryg114 · 07-19-2013, 05:34 PM

Anything can be broken and nothing is idiot proof. If you know what your engine and transmission are doing you are less likely to be dead on the side of the road with $1000's in repairs and also being at someone's mercy to get you out of a jam. They know they got you over a barrel and many will take advantage. Diesels are hard on transmissions and sometimes they break. Lots of torque lots of vibration take their toll on a transmission.

Perry

withidl · 07-19-2013, 10:22 PM

Quote:

Originally Posted by perryg114

He is right. You want to keep that torque converter locked up and the best way to tell is to get something like a scanguage II that monitors things like transmission temp, slip ratio (1.0 is locked) etc. Computers are only as smart as people make them. Transmissions overheat real easy if the torque converter is not locked. If the temps start rising too fast then downshift. If that does not work take your foot out of it. If that does not work slow down and pull over with the motor running till the temps come down. If the transmission is hunting for the right gear lock it into the lower gear.

Perry

There is another way to confirm torque converter "lock-up". Just monitor the tachometer as I do; if you vary the throttle/engine power and the tachometer needle varies/moves as if on a spring then the torque converter is not "locked-up"; if the tachometer needle remains solid, i.e. does not vary/move (except with gradual increasing vehicle speed) then the torque converter is "locked-up".