I was reading the manual (yes, I am impatiently waiting for the truck to be built and come in), and was reading the section regarding 4wd, ESOF, 4h and 4l. Then I did some searching on the forum to get a better understanding of what exactly is involved with 4wd, and found a couple of very informative threads.

Is the following summarization valid to make?

• 4wd systems consist of a different transmission compared to a 2wd, that has an additional output in the (front, side, bottom)(?).
  
• The front tranny output goes into a transfer case.
  
  • The transfer case can be confused for a differential, because it has the same general shape, but internally it is not capable of letting either wheel have differing speeds like a standard differential, which is essential for your standard road conditions, like making a turn.
    
  • The transfer case generally has two internal gears: high and low.
    
  • The transfer case may or may not be able to shift between high and low without moving slowly.
    
• From the transfer case, power goes out to the hubs
  
  • Hubs are a coupling between your wheels and the transfer case
    
  • Their primary use is to disconnect or reconnect power from the wheels to the transfer case
    
    • You really only want your hubs locked if you NEED 4wd, as it will cause both of your front wheels to be locked together, and they must match each other's speeds.
      
    • This would be really crappy for making turns, and in 2wd, having them locked provides you no benefits.
      
  • Ford Super Duty hubs are either automatic or manual
    
    • Manual hubs require the driver to exit the vehicle, and physically turn the hub to lock or unlock it.
      
      • You may have to rock the vehicle, or move it backward slightly to successfully be able to lock the hubs by hand.
        
    • Automatic hubs lock and unlock via vacuum, and do not require the driver to exit the vehicle to lock & unlock
      
      • Being able to lock and unlock from the interior of the vehicle allows you to be driving when the lock/unlock operation occurs, making it a little more painless.
        
      • Locking the hubs will not work automatically if the vehicle is already stuck, you will still have to exit the vehicle.
        
      • Automatic hubs still retain the ability to be manually locked. However, depending on why you need to manually lock them, you run a risk of not being able to unlock them.
        
• Super duties can be ordered with either Electronic Shift on the Fly or Manual Shift on the Fly, depending on the model and packages ordered.
  
• Electronic Shift on the Fly (ESOF)
  
  • Primary control is through a **** on the dash containing locations for 2H, 4H, 4L
    
  • 2H (two wheel high): Standard mode for driving on the road. Putting it in this mode tells the transmission to stop sending power out the front, to the transfer case.
    
  • 4 wheel drive modes
    
    • Instruct the transmission to send power to the transfer case
      
    • Comes with automatic hubs
      
    • Changes the vacuum level going to each of the front hubs, causing them to lock, and each wheel will want to go the same speed.
      
    • 4H (four wheel high)
      
      • You can attain higher speeds in this mode (perhaps in theory, as high as you can go in 2wd, although by definition if you have limited traction, you probably aren't going to this fast).
        
      • Since you are changing gears in the transfer case, you can shift into 4H at a higher speed.
        
    • 4L (four wheel low)
      
      • This instructs an electric motor in the transfer case to switch gears, lowering your overall top speed, but increasing your torque, is good for going up or down hills, or while pulling a load.
        
      • Unless you have a specific need for 4L, there is no point in using it.
        
      • Can take extra time to shift, and may require you to drive slowly for a bit, depending on if the teeth mesh properly.
        
      • Ideally you would be driving from 1-5mph during this switch.
        
• Manual Shift on the Fly
  
  • Most of the properties of the ESOF apply
    
  • Instead of a **** on the dash, you have a shift lever in the cab of the vehicle.
    
    • The shift lever can be in 2H, 4H, 4L, and Neutral
      
    • Neutral completely disconnects the transmission from the front transfer case, and the rear differential. This is really nice in case you need to be towed.
      
    • There is no electric motor that shifts gears in the transfer case.
      
  • Comes with manual hubs.
    
  • Not available on the Lariat package and above?
    
• Pros and Cons
  
  • Manual hubs
    
    • Generally considered more stout. If much of your time is spent requiring 4wd, you might consider manual hubs.
      
    • Because they require you to exit the vehicle, they are much less convenient.
      
    • Can be locked even if you are already stuck (because you can get out and manually lock them).
      
  • Automatic hubs
    
    • Are considered far more convenient than manual hubs for the vast majority of drivers, since you don't have to exit the vehicle to lock them.
      
    • Automatic locking and unlocking will not work if you are already stuck. You must shift to 4wd before being stuck, else you may be forced to exit the vehicle to lock your hubs.
      
  • ESOF ****
    
    • Electronically controlled shifting via a motor in the transfer case.
      
    • Considered more convenient.
      
  • Manual Shift Lever
    
    • Does not require an electronic motor to change gears in the transfer case, which can be considered fewer things to break (in theory, as long as you don't abuse it, when it won't go into gear)
      
    • Gives the driver a true neutral option, where neither the front or rear wheels have power connected from the transmission. Ideal for being towed, and only recommended for being towed.
      
• Overall Notes (subject to one's opinion)
  
  • Longevity of the 4wd components ideally has the driver engaging the system on a monthly basis. This keeps things free and lubricated. Many failures can be attributed to the lack of drivers ever engaging 4wd modes.
    
  • For the average driver, who doesn't use 4wd often, ESOF on the fly doesn't have many downsides, considering you are still able to manually lock your hubs (for the scenario in which you are already stuck and need to get out).
    
  • One could say that for the average driver, they are more likely to be able to increase the longevity of the system, because it is more convenient to engage 4wd and keep things free and lubricated. If you have to get out and manually engage the hubs, the average person is much less likely to do so, leading to problems down the road.
    
  • Don't drive far on hard ground with 4wd, it puts stress on the transfer case, especially if you attempt to make a turn. You ideally want one of the wheels to be able to slip in this scenario.
    

 

A transfer case is nothing like a differential. Put your truck on a lift and look at each.

Transfer case power goes to the front driveshaft, which is connected to the front axle.

Also, hubs couple your wheel hubs to the axle shafts. Indirectly, to the transfer case.

Hubs (manual or automatic) do not cause both front axles to be locked to each other. You still have a differential to allow axle speeds to vary as you go around a corner (in 2WD).

Automatic hubs still retain the ability to be manually locked. However, depending on why you need to manually lock them, you run a risk of not being able to unlock them.

That was why I installed manual hubs. In 2 Super Duties, I had hub problems, mostly with failure to unlock. Only with a fully manual hub can you be sure that the hub is fully locked or fully unlocked.ESOF can be slow going into 4-Lo. Mine takes its good sweet time deciding when or if it will shift. This was true of both Super Duties and few Explorers I have driven. I would never pick ESOF over a manual shift/manual hub configuration.

 

The transfer case provides power to both axles- power to the rear can be disengaged by putting it in neutral.

 

Please see my comments in bold...