I'm looking at the 2017 F-150 XL (stX) and was just curious as the difference between the 3.15 Non-Limited Slip Axle Ratio and the 3.31 Electronic Locking Axle Ratio. What is the major difference and why would I need the 3.31 Electronic Locking?

 

Where do you live? An open diff(non limited slip) makes a 2wd truck totally useless on anything but perfectly dry pavement, in the rain, on dirty or snow covered roads and anywhere offroad the truck will lose traction and get stuck way too easily.

The electric locking diff gives you the best of both worlds, when unlocked you have the greatest highway driving safety and when locked you have the greatest possible traction for low speed maneuvers on questionable surfaces.

Now personally I would never select an axle ratio that high for a pickup truck but it does depend if you're buying this to haul stuff or just to commute.

 

The 3.31 will be better for towing and the e-locker will give you on demand traction up to 25 mph

 

The 3.31 is slightly better for towing. With the 6 and now 10 speed transmission there isn't just a whole lot of difference, even in mpg.
If you can afford it get the locking axle unless you are positive it will never leave the road or be in anything slippery.

 

I dunno...I've had the e-locker on my '13 and my '15, and I've never had a practical use for it. The standard traction control brakes the slipping wheel, which makes the open differential function like a limited slip. Very obvious backing up my driveway...with the left side on ice you can feel the ABS pulse when the wheel slips. As the ABS is pulsing, the truck accelerates rearward.

The $470 for the option would be of more use to me than the E-locker.

 

The Traction Control on the new F150s works fairly well with the open diff.

If you're looking at a 2wd, the E-Locker might not be too bad of an idea, but a 4wd it becomes a moot point, unless you're into sloppy mud or deep snow a lot.

Josh

 

I agree with Tom. On my current F150 I don't have a locking rear end & haven't missed it yet. We have had rain, more rain and freezing rain since I've had the truck, so far so good.
On my previous F150's I tested the locking rear end to make sure it worked, but never needed it.

 

Open dif isn't the same open dif that's in my '79. As Tom said, modern traction control handles a great deal of the issues by braking the spinning wheel. The numbers are just the trucks start-ability with a load. 6 speeds also have made the lower numbers more practical than in days gone by, but if you're towing often, or just want a snappier start, the 3.31 will give you a better kick.

 

I wouldn't say moot. Where we go hunting is all dirt/rock/gravel roads and one of the hills is a 12* incline. Couldn't make it up,in 2wd but clicked on the locker and it moved along no problem. Could I have done it in 4wd without locking, sure. But a 2wd would have had to make a run at it.

 

I think it goes something like this:
2WD
2WD + ELD
4 Auto
4WD + ELD
Get out and walk! Call a tow truck.


Actually, according to the 2017 shop manual in either 2WD, 4Auto or 4WD High the ELD can be engaged at speeds up to 19 mph and will automatically disengage at 25 mph and reengage when speed drops to 19 mph.


In 4WD Low it will engage at speeds up to 56 mph and disengage at 62 mph and then reengage when speed drops to 56 mph.


It also states that under "certain circumstances" the traction control system can deactivate the ELD to protect the drivetrain.


So, if you think about those numbers it would seem that it would be most useful when in 4WD Low. Of course at 60 mph in low range I imagine things are rather noisy and exciting!

 

Problem with locking the axle at high speeds is instability. Both wheels spin when the rear axle breaks free, which means you're going sideways in a hurry. I wouldn't want it locked any faster than 20 MPH.

 

ELD is like most options, great to have if you need one !

 

As of yet, I haven't used it on the F150, used it a pretty good bit on the SD, worked great. Not sure I'd fret to much over it if it wasn't on the options list of a vehicle I was interested in purchasing though.

 

The one time you need it real bad and you don't have it
Just saying

 

The e-Locker was nice on the F250. I would engage it any time it rained or snowed. I never needed it on the F150 as it seems to have better traction. Given a choice I would rather have an e-Locker than not have it.