Electronic Locking rear end ...
 

Am I understanding this correctly, I found a manual online (I do not yet own a 2019 F350 XL link: http://www.fordservicecontent.com/Ford_Content/Catalog/owner_information/2019-Ford-F-250_350_450_550-owners-manual-version-1_om_EN-US_05_2018.pdf pages 220 and 221) ... reading about the operation of the Electronic Locking rear end, it states that in 4H not to exceed 20mph, and in 4L not to exceed 56 mph ...is this correct? I cannot wrap my head around this, I have never used 4L for anything other than scaling my driveway curb ridge before having a chance to get out to clear it, I thought that 4L was used mainly for such 'dire' circumstances, I did not think that anybody would be in 4L at 55mph...and the 20mph limit for 4H ?!?! that's what, second gear??
basically this tells me that I can expect to go through winter with open axles, I might as well not opt for the locking differential (except that I want the 4.30s and I may use it on occasion)...my '95 had limited slip front and rear axles, my '04 has only the offered rear, it looks like I will be driving 'solo' after I get a '19...did I misinterpret the manual or is what I stated the way it is...does anybody have this setup?
...also, I plan on ordering the manual transfer case, in a previous thread it was stated by (sorry, I cannot remember the name to give credit) that with the manual transfer case the electronic rear end is activated by a '2WD-style dash switch' however the manual does not address this either way, they only address ShifOnTheFly and 2WD...
...any explanation and setting me straight would be appreciated. Thank you.

...as in reversed, BIGDOG1974 ?

Yeah I saw that in my manual and thought yeah right.;)

Thanks, guys, any confirmation on the engagement with the manual transfer case?

My '18 with manual transfer case has a switch on the dash. More intuitive to use than the pull on the auto rotary knob on the ESOF transfer case..

Thanks, MBuckholz, the poster previous to this thread said that, I needed to confirm, this pdf manual that I found seems to be riddled with issues...another question since you have this hardware, so, I engage the rear end by turning the switch to ON, it activates and after a certain speed de-activates...the switch is a hard ON/, hard OFF, so if I drop speed I assume the rear end locks again, and this continues until I turn the switch to OFF or shut the engine? or does the rear end call for it to be locked 'forever' as long as the switch is in the ON position...?

No, it is not a typo at all. Your rear locker can be engaged at speeds of up to 20mph and it will automatically disengage right around 25mph, and automatically reengage at about 20mph. Your message center will warn you of this. Low range is not restricted. 56mph would probably be top speed, 6th gear, at redline in low range. The previous generation of Super Duty did not list a speed cut-out at all in low range, but it did in high range.

By the way, you cannot leave the locker engaged all the time. It really is for off-road use. The reason it automatically cuts out at speed in high range is because you could lose control of steering with the rear end locked...and stability control cannot work with the rear axle locked.

The limited slip is better for just trying to get moving in normal driving on snowy roads; the locker is much better for true off-road use. Personally, I love the locker. And yes, your manual transfer case will still include a knob in the usual ESOF spot but it will only turn "on-off" instead of the pull-out lock on ESOF.

If you leave the switch on, it will stay locked as far as the message center is concerned. What actually happens in the differential when you switch the locker on is a thick pin slides through the carrier side gears to lock both axle shafts together. This is done via an electromagnet or solenoid; I'm not sure on a Ford. But if its an electromagnet, the pin would disengage when the engine is off. It might with a solenoid as well. But as soon as you restart, it will immediately attempt to re-lock, which it should be able to do since the pin and hole openings are aligned.

You'll also find out the locker does not engage and disengage instantly...it needs to align the pin and holes, so sometimes some revolutions are needed, or torque load needs to be reduced.

If you want something that will give you the extra traction all the time, order it with the open diff, then put a Detroit locker or Truetrac in it after you get it.

Thanks, troverman and 00t444e...I wasn't looking for something locked all the time, just trying ti\o understand it, I would prefer a limited slip but they appear to offer it only on the dual rear wheel models.
So, for all practical purposes I will be doing my winter driving with open axles, the 20mph limitation will be useful for only so far...is there any other traction control within the factory four wheel drive system that would manipulate the wheels that are spinning and those that are not spinning?? It seems that Ford steers clear from marketing their four wheel drive systems to winter drivers, everything is always about rocks and sand, must be a matter of liability ...

For winter driving once you are above 20 mph, there aren't many situations an open front and rear diff won't get you through. I used to have a Ranger with an open front and rear and it would still go anywhere in the snow in 4x4 high.

As I outlined above I have had only two 4WD vehicles, the F150 had both axles limited slip in '95 with only the rear on the F350 in '04, I guess I never had the opportunity to find out if open front and rear would work well...I do use snow tires in winter so I have that working for me...so these trucks do not have anything in play that uses wheel spin and ABS to control the traction or slippage ?

They do have traction control but in my experience traction control is more of a hindrance than a help in the snow or ice.

Got it, thanks again, 00t444e