ESOF - shifting from 4H to 2H after a driveline "bind"

[KH_59]

The only other 4X4 I've owned had manual hubs and a manually shifted "stick on the floor" transfer case. In winter driving on patchy roads with the front hubs locked, I was pretty good about shifting the transfer case back to 2H just before hitting long dry stretches of road. But.....,occasionally..... a slight bind would occur and you had to overcome a higher effort at the transfer case stick to get it out of 4H. No big deal, and you could feel exactly what was going on and deal with it.

With the ESOF transfer case (not "advanced" 4x4) and, presumably, IWE disconnects at the hubs.......... how finicky do we expect the system to be when we're trying to electronically shift from 4H back to 2H if we have screwed up and let get into a bind on "dry" pavement? Will we be looking at a blinking "shift in progress" message until we pull off into a parking lot and do backwards figure-8s or some other gyrations until the damn thing goes back to 2H?

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[Mattwings]

Not in my experience. It does have electronic parameters it seems, but I have forgotten about shifting out of 4x4 when pulling on to the road and it has always made the change fairly quickly on pavement.

 

[Squatch]

I never had to do anything funky in my 2017 F150 like when my parents had a 1992? Explorer and had to back up in a straight line for 30 feet or something. I hope the Bronco is also just as easy.

 

[Laminar]

The ESOF transfer case on the F150 has a clutch inside of it that gradually connects the front driveshaft to the rest of the drivetrain. The TCCM (Transfer Case Control Module) actually does more than you realize. On decel, it disengages the 4x4, allowing you to coast through a corner on pavement without binding, though if you hit the gas, it will grab and squawk those front tires. There's more modulation there than you'd think, it is not a mechanical lock.

Because you're not pulling gears apart or dealing with a binding mechanical connection, there's no additional effort required to disengage. The clutch just separates.

Now the Raptor does have both the TOD clutch and also a mechanical lock. We don't know for sure if the Bronco will get that same setup, you can read about it here:

https://www.sae.org/news/2020/03/ford-raptor-unique-front-driveline

 

[rtaylor]

Will we be looking at a blinking "shift in progress" message until we pull off into a parking lot and do backwards figure-8s or some other gyrations until the damn thing goes back to 2H?

You shouldn't have to do anything special, but it may shift faster if you release accelerator pedal temporarily. Also, don't shift if wheels aren't rotating at the same speed (or stopped).

 

[KH_59]

The ESOF transfer case on the F150 has a clutch inside of it that gradually connects the front driveshaft to the rest of the drivetrain..........

Interesting. Is that synchronization clutch used in the basic ESOF case (2H, 4H, 4L) to just match the driveline speeds, then the case "locks in"?

For sure the "advanced" transfer case (2H, 4H, 4L, 4A) has a sophisticated clutching mechanism that can shift power to/from the front drive as needed in 4A mode.

 

[Mattwings]

The ESOF transfer case on the F150 has a clutch inside of it that gradually connects the front driveshaft to the rest of the drivetrain. The TCCM (Transfer Case Control Module) actually does more than you realize. On decel, it disengages the 4x4, allowing you to coast through a corner on pavement without binding, though if you hit the gas, it will grab and squawk those front tires. There's more modulation there than you'd think, it is not a mechanical lock.

Because you're not pulling gears apart or dealing with a binding mechanical connection, there's no additional effort required to disengage. The clutch just separates.

Now the Raptor does have both the TOD clutch and also a mechanical lock. We don't know for sure if the Bronco will get that same setup, you can read about it here:

https://www.sae.org/news/2020/03/ford-raptor-unique-front-driveline

That's one of the better write ups. I thought I had read a quote from Ford that the advanced transfer case was taken from the Raptor, but I can't find it anywhere now (another "fact" I thought I had verified that may be supposition). I wonder if the Warthog will have the torsen front limited slip? Seems like a interesting set up and what I would prefer.

 

[Laminar]

Interesting. Is that synchronization clutch used in the basic ESOF case (2H, 4H, 4L) to just match the driveline speeds, then the case "locks in"?

I didn't think so, but the article I posted makes it seem that way. The wiring diagrams for the F150 ESOF TC show a clutch, same as the TOD case. I have my old ESOF TC sitting on my garage floor, no one wants to buy a 260,000 mile transfer case. Maybe I'll tear it apart just to check out how it works!

 

[Flourman]

Regardless of t-case, I’ve always let off the gas when shifting. From 2H to 4H and then back.

 

[KH_59]

Found some descriptions online. Presumably, these same Borg-Warner designs are currently being used:


Electronic Shift-On-The-Fly (ESOF) System
The ESOF transfer case system consists of the following components:

• MSS , located on the instrument panel
• Transfer case assembly (includes shift motor and synchronization clutch)
• TCCM

The Borg-Warner 4469 electronic shift transfer case is a 2-piece magnesium design. The unit transfers engine power from the transmission to the front and rear axles. Vehicles equipped with an ESOF system allow the operator to choose between 2WD (2H) and 2 different 4WD modes. The transfer case is shifted electronically based on the MSS position. Under normal driving conditions, the transfer case is in 2WD (2H), but when desired, the operator may shift into 4WD high (4H) or 4WD low (4L). The operator can shift between 2WD (2H) and 4WD high (4H) at any speed. When shifting into or out of 4WD low (4L) range, the TCCM requires that the vehicle speed is less than 5 km/h (3 mph) and the transmission in NEUTRAL.
The transfer case is equipped with an electronically controlled high torque capacity clutch which is located inside the case. This clutch is used to synchronize the speed of the front driveline with the rear driveline during 2WD (2H) to 4WD high (4H) shifts. The transfer case is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.


2-Speed Torque-On-Demand
The 2-speed torque-on-demand transfer case system consists of the following components:

• MSS , located on the instrument panel
• Transfer case assembly (includes shift motor and synchronization clutch)
• TCCM

The Borg-Warner 4467 2-speed torque-on-demand transfer case is a 2-piece magnesium design. The transfer case transfers engine power from the transmission to the front and rear axles. Vehicles equipped with the 2-speed torque-on-demand system allow the operator to choose between 2WD and 3 different 4WD modes. The transfer case is shifted electronically based on the MSS position. Under normal driving conditions, the unit is in 2WD (2H), but when desired, the operator may shift into 4WD high (4H), 4WD low (4L) or 4WD AUTO (4A). When shifting into or out of 4WD (4L) range, the TCCM requires that the vehicle speed is less than 5 km/h (3 mph) and the transmission is in NEUTRAL.
The transfer case is equipped with an electronically controlled high torque capacity clutch which is located inside the case. This clutch is used to synchronize the speed of the front driveline with the rear driveline during 2WD (2H) to 4WD high (4H) or 4WD AUTO (4A) shifts. The clutch also provides torque to the front driveline in all 4WD modes. The transfer case is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.

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