2012 F150 3.5L Ecoboost 3.31 non-limited Slip vs 3.55 Electronic Locking Axle - MPG vs Snow / Drift
 

Hey all,

A Few quick questions my search did not come up with anything,

West Centeral Iowa and I'll be special ordering my 12 Eco Boost Super Crew Lariat - Main use commute to work 30+ miles in up / down hill / flats / county roads in Iowa, Family of 5-6 - no plans on pulling any campers , trailers , in the near future if anything once in a blue moon helping someone with a smaller trailer is the only thing I could think of.

Currently my setup is the 3.31 with NON limited Slip axle which is default for 2012 Eco 4x4 - if i wanted the Electronic Locking axle it would be 3.55+

My question - a few years ago 2006 Dakaota V-8 quad cab - ran into a drift into town - high centered ( Idiot move I know) rear wheel just spun the loose one, put into 4x4 - nothing front one spun as well. I just rather have both back tires be spinning in a situation like this OR when putting into 4x4 having the highest probablity of getting out of a stuck situation or if my wife and kids ran into an issue like this - maybe the truck sucked who knows.

2nd concern is MPG - This is an upgrade to my car (for several reasons) and the Ecoboost seems to have the boost and power I'd like in a truck with the best chance of MPG.

How much is the difference if very minimal MPG , is it so little but the gain of the 3.55 with electronic locking the way to go?

Can anyone shed light on this over the next day or so as the order will be placed. It's only going to be a $470 upgrade but again I travel back and forth 100+ miles a week and gas isn't getting cheaper.

Thank you

I have a 2012 4x4 Crew Eco with the 3.55 electric locking rear axle, I have used it a lot while Ice fishing last winter and it make a big difference for traction on glare ice conditions, I would go with the 3.55 in a 4x4 reguardless if you go with the locker or not, I see 18-22 mpg with the cruise at 62 almost always, a strong headwind or driving faster drops the mpg down in a hurry, my last 2 trips I was lucky enough to get a 20-25 mph tailwind and the mileage was 27 mpg at 62, the wind really affects these trucks.

I have 3.31's with the open diff and it hasn't had any problems tackling everything Maine winters throw at it. I go up north often and travel unplowed logging roads with 12"+ snow and even with the truck dragging I haven't gotten stuck. Even the open diff trucks have traction control so you don't get the 1 tire spinning effect, if just 1 tire spins the brake is applied to that wheel which in turn puts power to the opposite wheel. It's a very good system so I think you'd be fine with either choice.

First off, welcome to FTE!

I have a 2011 EB 4x4 with the 3.31 axles. I live in SE Virginia where the weather is very mild by comparison to the snow belt.

I have 12K on my truck now and I'm seeing 20 mpg's mixed and easily 24 on the highway doing 70+. I don't currently or intend to tow, this set up was the obvious choice for me.

However,

I am from Maine and I remember the tough winters, ice, snow and no help for miles around. If I still lived in that climate or region, an E-locker or a limited slip diff would be a must, IMHO.

The idea of an electronic locker is great because it gives you the forgiving characteristics of an open differential on ice but the option to lock up the axles for traction when needed. Only problem is it shuts off above 20 MPH. That's only good for starting up from a stop and worthless for powering out of a bad situation. I've thought about searching for a wiring diagram and rewiring it so when I switch it on it stays on.

So in this situation...wouldn't a limited slip be best since the E-lock disengages above 20 mph??

So the only options offered in 2012 is Non-Limited Slip axle or Electronic locking
Axle.

What is considered a "Non" limited slip axle compared to "A limited Slip Axle"?

Thanks for the replies!

Depends on road conditions, personal driving style, and the skill level of the driver. There is no single best answer. I know people that can drive a 2WD truck through conditions I wouldn't even dare try with a 2WD.

In my example, I drive icy roads in winter and it is not likely that I will need to drive deep snow because I'm on maintained roads. I want the e-locker because I'd rather have an open differential most the time. I prefer to have just one tire spin and the vehicle stay straight. It's what I'm used to and the way I want a vehicle to handle. If a truck with limited slip spins back tires then the rear can get squirrelly because you have total loss of traction. I have friends that want the limited slip because they like the ability to twitch the back end on command. I'm not that adventurous and, frankly, not that skillful to be messing with throwing the back end around.

If I was driving deep snow or slush I'd probably want the limited slip because I'd want both rear tires pushing at all speeds. But basic 4WD is probably sufficient for nearly any situation. And if it's not then you have to wonder why you're trying to drive though it?

Limited slip diff (LSD) is just that. It does have one main drive wheel, the other wheel will engage after slippage has been detected on the drove wheel.

Non limited slip has one drove wheel no matter what the situation dictates.

I've had both and were satisfied with both.

You are buying a Lariat which comes with full-time 4WD (4A) where you have the ability to drive in 4x4 mode in any conditions - dry, wet, ice, snow, mud, etc., and nothing should bind up on you.

I believe the difference in fuel economy would be nominal between the two gear ratios and it seems like many go with the 3.55 as a happy medium to get the locker and fuel efficiency.

Best of luck!

So the 4A is an all wheel drive function?

The 2012 lariat I tested had options....
2H,
4A,
4H,
4L.

4a Is the "Auto" function, when the system determines the rear wheels are spinning it engages the front wheels to help out, when you are in the "Auto" position the front hubs stay engaged so your front axles are turning but they don't pull any load until the system determines it is needed. The transfercase does the automatic engaging when needed.

Well that is really cool! So this would be a great way to keep maximum traction in the snow?

if it works anyway like the chebbies ... it is the best way to get the best traction in *variable* conditions. say, 50% clear 50% snowpack.

in the deep stuff, you will get better traction in 4h.

that is, if it works like other brands i have driven. it is possible that they use a different means to make the 4A work.