Hi all,

First-time pick up truck owner here. My 2012 F-150 is 4wd and has "2H, 4A, 4H and 4L" on the "gear dial".

I live in a pretty wet part of the country. Sometimes I'll drive in snow and I plan on using 4H for that.

I understand 4H and 4L and 2H. I know that in 4H the truck is always putting power to both of the axles, so at least one wheel in front and one in back have power all the time. I know that 2H is power is only going the rear axle all of the time, so one wheel in the rear has power all the time.

Is 4A like AWD? Meaning, only one wheel has power all of the time, but that the truck is switching back and forth between the front and rear axles? If it's in 4A, will the truck sometimes give power to both axles?

For dry pavement, 2H is the way to go. However, for wet pavement is 4A better? Will my gas mileage be any different for 4A vs. 2H?

Thanks! I'm still learning about 4wd. BTW, I am so happy that I bought an F-150. It's about the best purchase I ever made. What a blast to drive down the road.

 

4A is auto 4x4 meaning it's in 2wd until the rear wheels slip, the it puts power to the front wheels so you don't lose control

 

Thanks for the info. Will operating in 4A cause my gas mileage to be any lower than driving in 2H? I don't think that it would because the truck would still operate as now 99.99% of the time - power goes to the rear axle.

It sounds like 4A would be safer than 2H in wet pavement - if the rear wheels lose traction, the front wheels would get the power.

 

I'm fairly certain that 4H splits torque 50/50 front and rear. 4A is an auto torque split with an initial bias to the rear axle, but I think 4A also locks the front axle. I only say this because I was driving around in 4A and the front end started pushing when I was turning as if the front axle was locked. I'd say 4A for most limited traction conditions on the road, 4H, and 4L for off road.

 

Yes.

 

There is a treasure trove of information in the owner's manual.

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Goth 150
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I am doubtful that the front is "locked". If it were locked, it would actually pull hard to the inside of the turn and not push. Automatic mode is for the questionable times of needing more than the rear axle. If you live in town and drive in the winter, 4A is likely the better mode so that the vehicle behaves very similar to 2WD mode, but with improved traction. If you have noticed the 4WD mode in town, it usually fights you when you turn sharp and the front wheels want to scruff all the time. I like it for going to the mountain in the winter so I can use it in the transition zone from wet to frozen road surfaces.

 

I have about 4K miles on my '12 F150 4x4 and have driven 99.9% of those miles in 2h only. MPG around town have been around 14.5. The other day as I was driving around 40mph I decided to switch to 4A and drive in that mode for a while. The first thing I noticed was the instant gas mileage graph jumped up immediately... Off the chart. I'm going to track this for a while and see if this holds up. My wife took my truck to work yesterday so I don't know where it stands.

I wonder if the drivetrain operates more efficiently in 4A, thus improving rather than diminishing MPG... seems counterintuitive...

 

Im not realy sure there is a point of using the 4A on anything other then snow. If the advac track system since slip on any wheel it will cut power and hit the corresponding brake to bring the vehicle stright. It just seems kinda pointless to ride around in 4A.

 

...

 

Ok, my wife has been driving my truck all week in 4A. Mostly stop and go traffic... Mileage per truck calculation is holding steady at 16.1mpg where it had been 14.5 in 2H.

I just ran a local errand and put the dash monitor in the mode where you can see the amount of power being applied to each wheel. I'm thinking driving in 4A is actually more efficient, especially in stop and go traffic. When accelerating power goes equally to all 4 wheels. Doing so gives a push and pull effect requiring less energy to get moving. This is all pure conjecture and absolutely unscientific, so feel free to shoot holes in my theory.

When you get on it from a stop it seems to put a little more power to the front wheels than the back. Not a lot but more based on the gauge. Again, the drivetrain isn't having to push the truck completely but rather evenly distributing power and in my unqualified opinion more efficiently. Acceleration feels more solid and controlled as well.

She is about to take a couple hundred mile road trip tomorrow, so I'll get to see how it does with highway driving.

 

My FX4 only has 2H, 4H, and 4L. I wonder if I can swap out the switch to gain the other settings or if there's more to it than that?

 

There's a LOT more to it than that - a whole different transfer case.

 

Driving around in 4A is not in and of itself going to make your truck more efficient than 2wd. When the 4a is engaged, the transfer case remains partially engaged which leads to parasitic loss. I would say that there is something else contributing to the bump in mileage.....

 

That was my thinking before... But it seems like the truck rolls more freely in 4A than 2H almost as if there was more parasitic loss in 2H.

In 2H the front transfer case is just dead weight creating drag (hence the typically lower mpgs in 4wd vs. 2wd vehicles). In 4A it is working with the rear drive rather than against it... It appears to be highly computer controlled, more so than traditional 4H, utilizing the front as needed rather than constantly.

Time will tell I guess...