Hello - I've had some recent IWE issues (thankfully covered under warranty) and with the weather turning to snow, it's got me thinking about 4x4 usage in my 2018 3.5L ecoboost. I've read the manual concerning when to use the 4x4, but I have a few questions and am curious for input on how and when you all engage your 4x4...

First, in the manual and at the service dept I've seen/heard mention of the truck being in a different "gear" when it's in 4x4 (either 4H or 4L) but I've always associated the word "gear" with the transmission when it's in normal drive mode (for example, one of the 10 gears automatically selected depending on what speed you're driving). When I switch to 4H, how is that "gear" different from the other 10 gears?

Also, I know the manual says 4H is for use in deep snow, but around my parts it seems even a little snow on the roads can lead to really poor traction for the truck. So, I typically will switch it to 4H as soon as I can tell my traction is getting poor (unfortunately my truck isn't equipped with 4A). For example, I've been switching into 4H if I'm driving across town in a snow squall to get the kids to school. However, the roads aren't always 100% covered in snow and I find that as soon as I start trying to make too many turns (for example, navigating around a snowy parking lot) the truck starts to really shudder and shake. I know the shuddering and shaking is typical of being in 4H, but should I be more diligent about switching out of 4H? Does anyone else switch it out of 4H when parking even if the lot is covered in snow? How often are you all working that 4x4 **** while driving? Do you find yourself deliberately making really wide turns in 4H to try and avoid the shaking?

Another scenario I've been in is driving on the highway during a bad snow storm where snow is drifting across the road and some parts of the road are snow packed while others are dry pavement. If I'm going 50-60mph, how often should I try to be switching in and out of 4H? My concern is that I'll be on dry pavement for a few miles but then all of the sudden encounter a snow packed section and will need/want it to be in 4H.

Lastly, I'm curious how often you use 4L as well as the locking rear differential? Judging from what it says in the manual, I'd have to be pretty adventurous off road to need either of those options. Anyone have examples of when these options have come in handy? I'm thinking I should at least test out 4L and the locking rear differential but I'll need to find somewhere off-road to go...

What confuses me from the manual though is that in one part it says the the rear locking differential "will not engage if your vehicle speed is above 20mph" in 4H but then it goes on to say it won't engage if "your vehicle speed is above or 56 mph" in 4L. It also says that "in 4L (4x4 low) the electronic locking differential will automatically disengage at speeds above 62 mph and will automatically reengage at speeds below 56 mph." I thought that 4L was only for speeds below 3 mph? Would the rear differential really be locked if I'm going 50mph? Does anyone drive in 4L at those higher speeds? Perhaps this is a typo in the manual?

If you've made it this far, thanks for reading and please let me know your thoughts! Apart from the IWE issues, I really love the truck and want to make sure I operate the 4x4 correctly and keep the truck in good shape for years to come. Thanks in advance for your input. I'm interested to see what everyones thinks...

 

The simple answer, when your stuck, put it in 4wd to get unstuck.

4 low is for off road conditions, stuff like rock climbing. You will never need it if you don't go off road. Use 4 high in the snow, ice. The snow covered lot was ok for 4 wheel drive. Even in snow you can't make tight turns, avoid that. If the road is bare go with 2wd. Turning onto another road with snow just turn it on.

Use the E locker when in 4wd you still get stuck.

I think today people over use 4wd. With traction control you will be amazed how well it does in 2 wheel drive. It's snowing here today, but not really sticking, just a little slushy and in 2wd it works good, no need for 4wd.

 

IWEs are Independent Wheel Ends that disconnect the front axle drive halfshafts from the wheels when in 2H. This reduces wear on the front drive components and improves fuel economy. The IWEs use a solenoid valve which when open, provides vacuum to the IWE to engage it. When shifting on-the-fly from 2H to 4H, the TCCM (Transfer Case Control Module) uses a clutch inside the transfer case to increase and synchronize the speed of the front axle to the wheels before the IWEs engage. Any issue with the solenoid valves or vacuum lines while in 2H can cause a premature IWE engagement (without the TCCM getting the chance to synchronize speeds) possibly causing IWE issues. What all that means is you are more likely to have IWE issues from driving in 2H than in 4H.

Your truck has a 2-speed transfer case. In 4H the "gear" ratio between input speed and output speed is 1:1. In 4L the workings inside the transfer case are changed and the "gear" ratio is changed to something less than 1:1. I'm not sure what the speed reduction is, but its roughly 2:1. These transfer cases actually use chains and sprockets. 4L is used for rough terrain, slow operating of the truck on steep hills, pulling a trailer off-road, etc.

Use 4H whenever you feel you need extra traction because of snowy or icy road conditions. Do not use any 4 wheel drive for an extended period of time (unless you have 4A) on dry paved roads as this will cause binding in the drivetrain. Definitely switch your drive mode from 4H to 2H when on the highway and dealing with snow covered patches. Don't worry about a little jerking while performing tight turns in 4H (or 4L) on snow packed parking lots.

I rarely use my ELD (Electronic Locking Differential). In most cases, for day-to-day driving, the traction control system will control wheel spin. The ELD automatically disengages at higher speeds to reduce wear on the differential components due to tire size difference from side to side. Even though you have the same tires on each side of the axle, they may be operating with different rolling circumferences. Tire air pressure affects rolling circumference.

You are correct when you think you would need to be doing some real off-roading to need some of the features your truck offers. I very rarely use 4L and usually only shift into 4L about once a month to keep the shift linkage attached to the shift motor properly functioning.

Hope this helps you some and enjoy your truck.

 

To some degree the 4x4 system in modern trucks are close to idiot proof - basically, systems will not engage certain components unless certain criteria are met. But, they are not fool proof.

Here are a couple simple rules to follow. Don't use the electric locker unless on very slippery surface. Never a dry surface.

If you're in 4x4 making tight turns and the truck is "shuddering" or otherwise resisting making turns, you don't need 4x4 engaged. You clearly have plenty of traction, as the "shuddering" is actually a result of the inside tire(s) fighting to overcome traction while traveling a shorter distance than the outside tire(s)

4L is for offroad low speed control (e.g.; hill descent, as in muddy +15%). If you're not off-road, AND requiring extreme control of traction/speed, 4L is unnecessary. Most off-road conditions can be satisfied with 4H.

The gear referenced in 2H vs 4H vs 4L is the Transfer Case, which is after the transmission.

 

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Thanks for all the information. You are definitely right about the IWE issues in 2H. I brought it in to the dealer after noticing lots of noise just while driving normally in 2H. Almost sounded like when you ride a bike with a baseball card in the spokes. Very similar to the increased road noise when the 4H has been switched on. Turns out they replaced the entire IWE system (over $2,000 in parts, I was told). It was driving great after the repair until I had to switch it into 4H for a slick morning commute. Ever since then the sound will return when in 2H and then after a few miles will go away, whether 4H has been recently engaged or not. It seems to primarily happen after the truck has been parked (say, overnight in the garage or even just for a quick trip into the store). Once I start driving I notice the sound as soon as I get up to 30-40mph. The sound will persist for a few miles until apparently something disengages, the sound disappears, and the truck rolls along smoothly again. I'm bringing it into the dealer again to hopefully remedy the issue. At times it almost feels like I'm dragging something along, though I know it's probably just something with the IWEs.

 

Traction control uses your brakes to control wheel spin, so if you're seeing the traction control light flash quite a bit to control wheel spin it's more pressure on your brake pads, and maybe that's what 4 wheel drive is for. I look at traction control as a way for the software to help me recover from a mistake I made, not as something I want to rely on for slippery conditions to get traction.

 

I think most of your questions would be answered if you had a 4x4 Lariat or above trim with 4A.
I have a lowly XLT 4x4 that Ford in their 'ultimate BS wisdom' seen fit that all 4x4 trims below Lariat don't can't and probably never will have 4A.

Now to one of your questions with only 4hi part time 4x4 hi available on my XLT, on patchy snowy roads i keep switching from 4hi to 2hi depending on when i see slippery or dry pavement ahead.
The big problem, sometimes i forget when i'm in 4hi only to be reminded when i make a turn on dry pavement but then its too late the drive train has already been stressed which can't be good for long term drive train reliability..

Far as the elocker, its only meant for slow speeds below 20 or some mph.
I use it mainly for off road slow speeds or when at a stop with snow or gravel it'll get you going without the one rear tire spin syndrome.

As 4lo ridgedly locks both the front and rear axles in addition to increased torque via the gear reduction in the T-case should not be used period on dry pavement.
It can be use temporarily without turns on dry pavement to say pull a car out of a ditch, a boat out of the water, etc.

 

You can add 4a to lesser trims I've seen threads on it here.

 

This is true but based on the main post, I don't think the OP will be tackling that anytime soon.