1. What would be the situations where I would want the Traction Control button to be OFF? I'm assuming this would be some type of bad situation off-road??

2. My truck did not come with a rear differential lock (didn't get the FX4 package). How critical is a rear diff locker? About how much would it be to add it if I decided I want it from a local shop?

I believe my 2015 has the 3.55 Non-Limited Slip. Good enough? Not sure the difference between a Non-limited Slip vs Limited Slip differential. Looks like all new F150s on offer the choice of a Non-Limited Slip or Electronic Rear Differential Locker.

I've heard of folks saying you can "trick" the truck into acting like it has a rear locker by lightly pressing the brake and gas at the same time. What's that all about???

 

1) Trac Control off: I can't answer that on the F150, but on my FWD minivans and Taurus, I'd turn it off occassionally (just occasionally) on snowy roads because I felt I could feel the road better and use "Drifting" (driving drifting, not snow drifts) to my advantage.

2) Locking Rear axle: I have the 3.55 locking rear. A locker turns your 1-wheel drive axle into a 2-wheel drive axle. Since you have a 4x4 without lockers, you really have just 2WD minimum when the 4x4 is engaged. IMHO, that is equal to or slightly more useful than a RWD with locker (also a 2WD vehicle).

4x4 with locker = minimum 3WD.

You probably could have an aftermarket locker installed, but it won't be electronically linked like the OEM locker is. It will probably also void your powertrain warranty.

My 2 cents: Under regular use (assuming you are not a farmer nor using the truck to pull equipment trailers on a construction site) I think you should wait until the powertrain warranty expires. If in that period of time you find you had to call a tow truck to extract you (i.e., 4x4 wasn't sufficient), then spend the hundreds of dollars to have a locker installed.

I have it just-in-case since I'll occasionally be pulling a car hauler (with AMC Jeep CJ loaded) in muddy areas.
Note: the locker is available without the FX4 offroad package.

 

Good read on how differentials work:

http://auto.howstuffworks.com/differential.htm

 

I have a swamp buggy on 48" tractor tires 4x4 of course. It was open diff front and back. I welded the rear diff (never sees concrete), now I never lock the front end. Welded rear is better than 4x4 with open diffs in my case.

 

yep, what moguy1973 said... and you will be fine. You dont need anything else.

 

There are some videos that someone posted a while back when I was truck shopping that helped me visualize how differentials work. They were Jeep brand videos with their terminology, but it was easy enough to translate it to Ford.

I got an 3.55 with e-locker because it was on the truck that I wanted. It wasn't a deal breaker to me. We get some good snow up here at times, and maybe I'll use the locker if I am really in a bad spot, but who knows if I'll ever actually need it.

 

$1200 is more than I would be willing to spend for e-locker. I was thinking $300. Oh well.

So what you're all saying is my truck is fine the way it is and don't screw with it?

 

I don't have nearly the towing, or 4X4 experience that many of the members here do, but I've owned a Expedition 4X4, a Nissan Armada 4X4, and an Infiniti QX56 4X4 all setup for towing. I never ran into a problem towing anything and getting stuck. When running up in the mountains for skiing, etc... I bring chains for all 4 wheels.

For 2WD, other than mud and snow, two other reasons for a limited-slip or locking diff that have happened to me are:

1. Towing horses on a slight uphill grade, and finding that the tall grass is covering soft earth.
2. Heavy boat on a slick, mucky boat ramp.

I think you'll find out your 4X4 will be great. BTW, I've used the light braking trick but can't confirm if it really does anything to improve already good 4WD traction.

My buddy, and my brother had 2014 4X4 F150's with the electronic locker. I just had to have it. Now I do.

 

Yes. Leave it the way it is. Check out the The Fast Lane Truck video of them driving through 10+ inches of snow without any troubles.

 

I think you are fine for nearly everything (if not everything) you will encounter. I have it for those times I'm trying to pull a 7,000 lb tandem axle trailer in mud.

My 2 more cents:

Separately but related, here are some thoughts on advice someone else gave you above:

1) An aftermarket E-locker referenced above is not the same functionality as a 2015 OEM locking diff. The aftermarket E-locker referenced above is electronically manually engaged/disengaged by the driver. The OEM locker is automatic and will disengage on it's own (e.g., at higher speeds) after manually engagement by the driver.

Furthermore, some people complain about aftermarket selectable lockers and say if you want selectable aftermarket, an ARB air locker is the only choice (this is ~$1000 parts only).

2) Advice was given above that the 2015 F150 is an 8.8" may or may not be true.

Summit Racing says it is 8.8" 31 spline: http://www.summitracing.com/search/y...ntial-carriers

However:
- US Standard Gear Diff Wizard says it is a 9.75":
http://www.usastandardgear.com/diffwizard.aspx
For example, here's their 3.55 replacement ring & pinion for the 2015 F150:
http://www.usastandardgear.com/produ...x?ProdID=13173


3) An aftermarket E-Locker referenced above may very well be $1200 installed. But you can get a locker cheaper than that if you are dead set on replacing your brand new rear diff. (which is probably not necessary).

http://www.summitracing.com/search/y...ntial-carriers shows different limited slip and lockers.

They sell for $319.27 a USA Standard Gear SL F8.8-31 - USA Standard Gear Spartan Locker. This will engage/disengage on it's own and it will naturally be noisy. It won't have the benefits or features of an Eaton E-locker or the even better Ford OEM locker, but it will be a locker (still though, I wouldn't spend the $319.27 to upgrade your new truck's diff since you will rarely have a need for it).


4) Finally, If you really, really, really want to do something to upgrade your new truck's rear end, perhaps an aftermarket limited slip diff would be appropriate and not noisy like a regular locker.

As an example for comparison and illustrative purposes only (I'm not making a manufacturer recommendation), here are two different 8.8" Yukon examples:
- http://www.summitracing.com/parts/yg...rd/model/f-150
- http://www.summitracing.com/parts/yg...rd/model/f-150


That's 4 cents total from me.