Rear locker vs 4L

[Armin]

Hi all,

In short I'm wondering how the new rear locker option compares to the 4x4 4L option on steeper icy hills.

To add some context, I currently have a 2017 Limited, hence previous gen, model and use the 4x4 a lot in combination with some M&S tires. I even get to use the 4L a few times a year to crawl up and especially down some icy hills in my neighborhood. But I learned to my dismay that the 4th gen only offers 4L on the FX4-package unless you get HD tow.

When I price and select the options I'd like I again would arrive at a Limited. For some reason for FX4 I then must take 301A and cannot take any of the other 3 packages. Alternatively I'd could get HD tow, or forgo the 4L. I'm reluctant to get HD tow as it would basically be hurting my fuel economy and highway drive experience. It is one thing to pay for something you don't use - I tow only light loads - it is another thing to pay extra for something which hurts me the other 360 days a year.

So I've been looking at the new rear locker option. I know it is not a real locker but more like a hydraulic disk system that can overheat when used continuously (e.g. the infamous TFL video) but that won't apply to me, as I will be using it only in short bursts. My guess is that it would work uphill pretty decently as an aid to 4x4 snow mode. But I'd love to get some experiences from people who actually own and used this option.

And, then there is downhill. I'd doubt it would do much compared to 4x4 high/snow mode, but open to be corrected.

And what about hill decent control? I must admit, until this weekend I've always had a bias against these systems. I used it once many years ago on a Nissan in the Australian rainforest, and it failed so miserably I never bothered. But with the above in mind I gave it another look on some icy dirt roads during a weekend trip. It seems these systems have improved, but I'm still skeptical. The roads I tried it on, I could have navigated in 2H with manual L1 gearing if I made effort, so have not convinced me that when I really need 4L this would also do it. So if anyone has some actual experiences I'm all ears.

 

[MxRacer965]

I always chuckle a little when people get concerned about gas mileage when driving a hulking SUV like these. If MPGs were that much of a concern a big SUV isn’t going to fit the bill there...

Anyway, if you want 4L and are worried about HD tow, I wouldn’t be. I have it on my 19 Max Platinum and I have no complaints. It’s quiet and comfortable on the highway, so I don’t know how it could be “hurting my experience”.

I have a 87 octane daily street/tow tune from 5 star and am getting average of 17MPG in a mix of suburban and rural driving between 45-55 most often. Maybe one a week trip on the highway.

I can’t really comment on the rest.

 

[carymccarr]

Hi all,

In short I'm wondering how the new rear locker option compares to the 4x4 4L option on steeper icy hills.

To add some context, I currently have a 2017 Limited, hence previous gen, model and use the 4x4 a lot in combination with some M&S tires. I even get to use the 4L a few times a year to crawl up and especially down some icy hills in my neighborhood. But I learned to my dismay that the 4th gen only offers 4L on the FX4-package unless you get HD tow.

When I price and select the options I'd like I again would arrive at a Limited. For some reason for FX4 I then must take 301A and cannot take any of the other 3 packages. Alternatively I'd could get HD tow, or forgo the 4L. I'm reluctant to get HD tow as it would basically be hurting my fuel economy and highway drive experience. It is one thing to pay for something you don't use - I tow only light loads - it is another thing to pay extra for something which hurts me the other 360 days a year.

So I've been looking at the new rear locker option. I know it is not a real locker but more like a hydraulic disk system that can overheat when used continuously (e.g. the infamous TFL video) but that won't apply to me, as I will be using it only in short bursts. My guess is that it would work uphill pretty decently as an aid to 4x4 snow mode. But I'd love to get some experiences from people who actually own and used this option.

And, then there is downhill. I'd doubt it would do much compared to 4x4 high/snow mode, but open to be corrected.

And what about hill decent control? I must admit, until this weekend I've always had a bias against these systems. I used it once many years ago on a Nissan in the Australian rainforest, and it failed so miserably I never bothered. But with the above in mind I gave it another look on some icy dirt roads during a weekend trip. It seems these systems have improved, but I'm still skeptical. The roads I tried it on, I could have navigated in 2H with manual L1 gearing if I made effort, so have not convinced me that when I really need 4L this would also do it. So if anyone has some actual experiences I'm all ears.

I have a navigator with the hd tow and two speed transfer (H/L). I get ~18mpg mostly around town. Rides smooth on the highway. No complaints.

Never tried the downhill assist.

 

[shane_th_ee]

The locker is NOT a replacement for 4L for steep, slippery descents like you’re describing. 4L works as a torque multiplier which greatly increases engine braking. Which is exactly what you want on steep, slippery descents. The rear locker just maintains torque at each rear wheel, during the application of power, even when one starts to spin.

 

[Armin]

@shane_t_ee, yes I understand. To clarify I was wondering how well this eLSD works going up. Downhill it will not do much, except perhaps keep me a bit more straight when the hill has bends.

I was hoping that the downhill assist would help enough, but wonder if that really adds something when push comes to shove.


And @carrymccarr and @MxRacer965, indeed fuel economy isn't great on our beasts anyway, but overall on the lifetime it would cost me extra and add stops at the pump. And that all for those few days a year I need 4L. Hence, why I was looking for alternatives. But considering every HD tow owner states their ride is fine, I'm perhaps just worrying too much indeed.

 

[Fizzy]

2020 Platinum, with HD tow.

How exactly does the HD Tow package hurt driving experience and fuel economy? I haven't noticed either...

 

[Armin]

It has a different axel ratio.

So that would mean higher RPM at highway speeds.

But correct me if I'm wrong.

 

[Fizzy]

Ohh, yeah - that makes sense. Haven't noticed anything untoward with ours. Just silky smooth sailing on highways. Doesn't feel like it's revving higher.

Frankly, to have the locker, and 4L, and to be able to tow almost 10,000 lbs, is worth the marginal bump in fuel economy. The thing is a beast anyway - worrying about fuel economy is like trying to apply a bandaid to a severed limb.

Dash says empty, I stick fuel in.

 

[minichunks]

The FX4 has the same 3.73 axle as the max tow. In theory, max tow and FX4 should have the exact same mileage

FX4 Off-Road Package with 360-Degree
Camera
$2,035
Available on XLT 202A and Limited 301A, the FX4 has all the essentials for your next off-road
adventure:
• Premium off-road front and rear shocks
• ControlTrac eLSD (3.73 Electronic Limited Slip Differential)
• Two-speed automatic 4WD with neutral towing capability
• Heavy-duty radiator
• 360-Degree Camera
• Fuel tank underbody protection
• Skid plates
• 18" Magnetic Metallic-Painted Cast-Aluminum Wheels
• P275/65R18 all-terrain (A/T) OWL (outline-white-letter) tires
• Platform chrome-plated running boards
• Front- and second-row floor liners
• FX4 badge
4x4 models only.

 

[shane_th_ee]

Hi all,

In short I'm wondering how the new rear locker option compares to the 4x4 4L option.... I'm reluctant to get HD tow as it would basically be hurting my fuel economy and highway drive experience...

Hold up a minute. The eLSD option is the 3.73 rear axle as a stand alone option. It's the rear axle ratio of the HD tow (and FX4) package that results in the drop in fuel economy. So if you check the eLSD box, you'll get all of things you don't want from the HD tow package and none of benefits.

 

[Armin]

@shane_th_ee - ouch that I did not realize. I did not realize eLSD gives you always the 3.73 even if you don't pick FX4 or HD tow, but in hindsight the description on Ford's website should have given it away.

If so that does make the choice easier for me, but not better. In essence it is then just a matter of forgoing 4L or just picking HD and accept the axel.


Nevertheless I'm still interested to hear experiences with decent control and the eLSD. But eLSD would then indeed be just an option in addition to 4L through picking FX4.

 

[Fozzy]

The Expy rear locker does a great job locking the rear tires together IMO. The off roading I have done I have had zero trouble. Pulling our boat out of the water is actually easier with the rear locked than in 4 auto or shifting into 4L. It does not offer the bulletproof lock of a pin lock style locker but it adds so much versatility for the inexperienced driver. It’s ability to be an open diff, limited slip or full lock is worth the money. If you have never driven a fully locked vehicle in the snow/ice. It is a hand full until you learn how it handles then you can actually get places to get you in trouble. I personally would rather have a vehicle with a locked rear than one with an open front and rear diff. Now add the ability to lock the rear and have the front engage, you can get places. Now with your occasional use in the snow and ice have you considered tire chains?

 

[vincentrose]

If you are worried about whether or not to get HD tow, let me tell you a story, back in 2002, I ordered a 2002 Ford Explorer, and ordered it with EVERY OPTION that Ford offered at the time, except the HD tow package, because I never did foresee needing it, since I was living with my parents at the time, BIG MISTAKE, fast forward about 13 years, I met my wife, fell in love, got married, moved out of the city and into the country, where I found myself towing a trailer like every week, and more often than not, my transmission was overheating, had to have Rear Diff rebuilt, and rear wheel bearings failing every year and needing replacement. NEVER AGAIN! Engine finally blew last summer, and I replaced it with the 2014 Expy that I have now (with the HD Tow package of course, lol) Every SUV or Pickup I buy in the future, will have the HD Tow package from now on. Live and learn!

 

[Armin]

I actually found this video which starting at 4:50 shows pretty much what I'm looking for. I know sand and ice are not the same, and this is with the standard tires that Ford placed on the FX4 (which are not as offroad suitable as I'd prefer) but it actually shows in this case that the rear locker is indeed adding quite some value in combination with regular 4x4. I suspect it also does pretty well in getting that boat out of the water or trailer of that wet grass.

But since currently eLSD means not just taking the 3.73 axel but also forgoing HD tow, it is all bit a moot point. If eLSD was like an and-and option I'd may actually consider it, but unless you take the FX4 it is currently an or-or. So it is 3.73 + 4L or 3.73 + eLSD and then I rather take with what is proven to work for me now. And turns out to be a bit cheaper too.

My guess is that too many wouldn't buy the FX4 anymore if you could also get HD tow + eLSD as separate options on other trim and packages.

 

[Calidad]

With all full sized trucks a rear locker is actually a really big deal mainly when your on off camber spots and limited traction even in 4lo your stuck with 2 wheel drive. My Sequoia got stuck several times even in some really basic stuff like slick driveway due to this. A rear locker makes you 3 wheel drive add the smart traction stuff and your 4th wheel gets worked by the system modulating the brake on spinning tire to push power across the front open diff basically letting the truck hunt for grip on the front end.

Down hill? In snow? Hill decent in any modern awd/4x4 vehicle Subaru or Expedition does two things it allows you to set tire / speed rotation and the system turns the tires constantly the object of the game is no locking up / skidding of the tires meaning if a tire slides its still rotating so directional control can be maintained and speed can be controlled. Vs old school brakes you lock up tires and turn into a 5000lb toboggan with zero control.

Using the rear locker down hill in snow would likely hamper the crawl controls ability to keep all 4 wheels turning independently of each other based on traction at each corner.Especially if you have a turn. Given crawl control/ hill decent looks at each wheel rotation status and works to keep each one turning while limiting speed.

 

[Expedition Dave]

When people are concerned about economy, I always laugh at the people who respond "who cares it is a big SUV!" It is one of the reasons I chose the Expy over other more reliable brands. YMMV.

Anyway the mileage loss with the 3.73s is minor--and may even save you some gas as it does not need to downshift going up inclines at highway speeds, especially if loaded or towing. Again, really hard to measure here. Also, if you +1 in tire sizes the 3.73s won't feel as sluggish on the road.

The FX4 package does add some weight from the skidplates, but again minor.

And there are a lot of reasons why lockers can be detrimental on ice and certain snowy conditions--almost too long to mention here but consider that a tire that is not spinning, but just resting on the snow or ice still has some traction. But if that wheel is spinning, it has none. I think under 90+% of on road snowy/icy-like conditions, you are better served with the vehicle diffs both "open" and the traction control/snow software control working through the problem sets.

Ever see the videos of guys doing smokey burnouts on dry ground, and a couple of guys just start pushing the rear end around? Or guys off-road on a camber, and as they spin the rear/front slides down the slope...

Remember part of driving on ice or snow is the ability to generate forward motion, but also to maintain direction and control from sliding. Snow tires and chains also help in turning and braking, and are the real deal if you want ultimate Expy (4wheel and 2 wheel) traction.

 

[Dice Roll]

Go drive one with the airplane gear, the drive one with the 3.73. You won’t waste another second worrying about any of this. Just get the tow pack and be done with it. The engine just doesn’t respond well to the high gears. Takeoff is sluggish. On your test drive, take notes on how often the higher gear will have you dropping gears on little inclines. The 3.73 will sit in 10th much more. It’s minuscule the difference in a 3.31 or 3.15 truck in 8th or 9th versus a 3.73 truck running in tenth as to the final effective drive ratio.

just get the tow package, with all the attendant goodies and be glad you did. Like the better transfer case.

I think they started offering the eLSD rear separate from the other tow package options. Be sure to get them all of that’s the case, like the brake controller, etc.

 

[Deadman]

Unless you run all highway speeds, then get the 3.31. I drive little highways and insisted on the 3.73's.

 

[shane_th_ee]

Go drive one with the airplane gear, the drive one with the 3.73. You won’t waste another second worrying about any of this. Just get the tow pack and be done with it. The engine just doesn’t respond well to the high gears. Takeoff is sluggish. On your test drive, take notes on how often the higher gear will have you dropping gears on little inclines. The 3.73 will sit in 10th much more. It’s minuscule the difference in a 3.31 or 3.15 truck in 8th or 9th versus a 3.73 truck running in tenth as to the final effective drive ratio.

just get the tow package, with all the attendant goodies and be glad you did. Like the better transfer case.

I think they started offering the eLSD rear separate from the other tow package options. Be sure to get them all of that’s the case, like the brake controller, etc.

I think the OP should get the FX4 package instead of the towing package and whinge until Ford gives in and gives him the Wrangler Adventure Kevlar AT tires.

 

[Armin]

FX4 would be fine, except I'm just not sold yet on the fixed running boards, plus the mandatory moonroof on the Limited.

But you all have now convinced me I should not worry about the 3.73 axel. So in the end it probably will come down to what price I can get, and indeed negotiate some better tires.