When to Use Low Gears?

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gtilflm

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Hi. Complete newbie to towing, etc. here.

My truck (2006 F150) has an automatic transmission. There's D (drive), but there's also 2 and 1. I've never used those, but I'm assuming 2 is "low gear" and 1 is "really low gear". Generally speaking, when would I want to use either of these? Going up hills? All the time when towing the TT?

Thanks!
 

Gary RV_Wizard

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When going down steeper hills, to help slow the vehicle and reduce wear & heating on the brakes. Slow down at the top of the hill so that you start the downhill side at a speed no greater than what you want to maintain going down. Manually shifting to "2" will help limit the speed by using engine compression to retard it. That is generally a good idea where the grade is in the 3%-6% range. On really steep downgrades, e.g. greater than 6%, you may need to shift to "1". Use the service brake pedal to slow down enough to shift to the lower gears.

The transmission will automatically downshift as needed going uphill. The transmission selector also has a button that disables overdrive - you may want to do that in certain terrains if the transmission shifts a lot between the top two gears. That could happen on a road through rolling hills.
 

Mark_K5LXP

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Do you have the overdrive button on the end of the shift lever? That's the one I would poke to toggle overdrive in/out when it seemed it couldn't figure it out on it's own.

Mark B.
Albuquerque, NM
 

gtilflm

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Yes, there is a button on the end of the shifter labeled "O/D".

So, basically is it like this?
  • Going Up/Down Hills: Have overdrive OFF and also possibly use 2 or 1 depending on the steepness of the grade.
  • Flats: Be in regular "drive" with overdrive ON
 

donn

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Do you have a copy of the owners manual? That will give you instructions on when and how to use the transmission.
 

Mark_K5LXP

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I've used first exactly once climbing a very steep drive, and I didn't want it shifting to 2nd. Selecting 2nd is more of a steep grade/slow situation too. I go between 3rd and 4th routinely, anticipating a grade up or down hill. At least for my workhorse if I'm going through mountain twisties, engine compression doesn't seem to have much effect at slower speeds even in low gear, so the predominance of manual downshifting happens more at cruising speeds.

You'll figure it out. You won't need to futz with it as much as you think you might. First few trips I watched MAF, load and other engine parameters to get a feel for the sweet spots, and from there you'll just "know".

Mark B.
Albuquerque, NM
 

Skookum

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The transmission should put you in the correct gear for going uphill. You'd want to use the shifter to select or "lock out" other gears depending on the grade, for example, if the transmission is indecisive and keeps shifting up and down, you'll prolong your transmission life and improve cooling by selecting the lower gear and/or shaving off a little speed and not letting the transmission shift up. When in doubt, run a slightly higher RPM, again, to help with cooling, especially for the transmission. Transmission cooling depends on airflow and fluid circulation, same with the engine and its hydraulic accessories.

On downhill grades, you want to use gears to assist with braking and maintaining your safe speed, which is generally a little slower than you ascended, and being mindful of any lower advisory speeds like on downhill curves. How fast did you go up the hill, and in what gear? You want to go down the hill slower, and one gear lower. You want to keep your foot off the brakes as much as possible, and when you do brake, do so intentionally. Never ride or feather the brakes as this generates heat and can damage your brakes, warp rotors, and rob you of stopping power when you need it. If you keep having to hit the brakes to shave off speed, grab the next lowest gear. It's alright if you're high in the RPM band, like 4k, 4500. Your "braking horsepower" from compression in a gas V8 tends to be high in the RPM band just like power is.

On those Ford transmissions, first turn off Overdrive if there is a switch. Then, start selecting progressively lower gears using the gearshift lever to downshift or lock in the desired gear.
 

gtilflm

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Thanks for the detailed reply! Is it a good idea to have overdrive ON while driving on long flats though to save a bit of fuel?
 

Mark_K5LXP

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"MAF load"???
MAF - Mass Air Flow. Load - ECU estimate of engine loading. Just a couple of a few engine operating parameters you can use to know how hard and how efficiently an engine is working. Back in the day a manifold vacuum gauge told you a lot but now with OBD you can watch just about anything going on with the engine and transmission.

Mark B.
Albuquerque, NM
 

Ex-Calif

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Thanks for the detailed reply! Is it a good idea to have overdrive ON while driving on long flats though to save a bit of fuel?
Depends. Lots of tips on going downhill but a little more on uphills and flats.

Many trucks will have a "tow" button. Anytime you have a significant trailer load you should have the tow button on. Depending on the brand it will remap the shift points to optimize performance and efficiency.

So the first thing to do when towing a load is to get the tow button pressed before worrying about the transmission gear.

On the flats if you can run steady with the O/D on and the transmission is not constantly shifting from "3" to O/D (often called 4th) then leave the O/D on. Otherwise it's perfectly fine to leave the OD off. You will get lower mileage possibly.

Going uphill it is also dependent on load and grade. If the grade is such that the rig will only do 50 mph for example, leaving the shifter in D may result in accelerating from 2, hitting 3 and then slowing down due to lack of power to maintain and the trans shifting back into 2. Generally this is called hunting.

At that point a better strategy my be shift to "2" and drive at 45 mph. You don't want to drive floored because it can be really hard on the engine to run at really high RPMs. I usually have the pedal like 90% to the floor with a "little left in the tank."

The most modern trucks (like mine) have 8 speed gear boxes. This just gives a lot of choices between "zero" gearing and max gearing but the principles above are the same. One particular grade and load may be 6th gear. Another might be 5th. In these trucks one almost always has a tach so one can keep the rpm safely below redline.

On non-tach trucks and RVs you have kinda play it by ear and how the engine sounds.
 

gtilflm

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Thanks for the reply. Our truck (2006 Ford F150) does not have a "tow" button/mode. So, here's what I've gathered at this point...

Up Hills: You basically want to be mindful of RPMs, and make sure overdrive is off.
Down Hills: Definitely have overdrive off. If it's a steep grade and/or we're pulling a heavy load, go to "2" before starting to go down hill to allow for "engine braking" to occur.
Flats: Best to have overdrive on so you get the best MPG.

Does that sound reasonable?
 

Ex-Calif

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Thanks for the reply. Our truck (2006 Ford F150) does not have a "tow" button/mode. So, here's what I've gathered at this point...

Up Hills: You basically want to be mindful of RPMs, and make sure overdrive is off.
Down Hills: Definitely have overdrive off. If it's a steep grade and/or we're pulling a heavy load, go to "2" before starting to go down hill to allow for "engine braking" to occur.
Flats: Best to have overdrive on so you get the best MPG.

Does that sound reasonable?

Yup. Unless on the flats the tranny is hunting still, then you may want to turn off OD.
 

Skookum

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In my opinion the deciding factor on whether or not to have OD on or off while towing on flat ground is transmission temperature. Most pickup trucks don't have a trans temp gauge so it's hard to tell. If you're able to get one, it might be a good idea if you tow heavy often. For 2006, you should get a light or warning if the trans gets too hot.
 

Skookum

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And if it is hot, for some reason, turn OD off?

If you get a warning, you'll want to do what the manufacturer specifies in the owners manual.

The idea with a trans temp gauge is, if you think you're OK in Overdrive but the trans temp gauge is reading higher (say, 200-220F) and you get cooler results (180-200) if you reduce your speed a bit and get out of OD, you'll want to drive to sustain the lower temperature. Your typical dash warning light usually comes on when things are bad, like 250 and the fluid starts cooking itself.
 

Ex-Calif

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And if it is hot, for some reason, turn OD off?

Amber lights are cautionary and if the vehicle still feels OK to drive it probably is to your destination.

Any red lights - usually reserved for oil pressure, coolant temperature and trans temp (if fitted) requires immediate attention. Like pull over on the side of the road and assess.

If it's trans temp, you might pull over for 15 minutes to let it cool down and then proceed at a slower speed in a lower rpm range to the nearest suitable shop.

This one got my attention - My kid had a temp light come on, kept driving and cooked the heads on his Blazer.
 

Zulu Kono

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Hi. Complete newbie to towing, etc. here.

My truck (2006 F150) has an automatic transmission. There's D (drive), but there's also 2 and 1. I've never used those, but I'm assuming 2 is "low gear" and 1 is "really low gear". Generally speaking, when would I want to use either of these? Going up hills? All the time when towing the TT?

Thanks!
I move my shifter around a lot when I tow.
Going down steep grades I'll shift all the way down to 2nd and
let the engine control my speed rather than riding my brakes.
I don't use overdrive at all when I'm towing unless I'm
on a pretty flat stretch of road or a gentle downhill grade.
 
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