Three wheel drive?
Thread Starter
Senior Member
Joined: Dec 2022
Posts: 608
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From: From Down River MI. Now Boulder City, NV
Pardon my ignorance, the ford build site specifies regular axle and not "open" as well as the window sticker
are we talking about the same type of axles? My understanding of regular is one wheel driven only.
I appreciate everyones knowledge on axles in this thread, didnt mean to start a fist fight over it
are we talking about the same type of axles? My understanding of regular is one wheel driven only.
I appreciate everyones knowledge on axles in this thread, didnt mean to start a fist fight over it
Senior Member
Joined: Jan 2012
Posts: 552
Likes: 362
From: Warsaw, MO
I did. If you pull over to an icy shoulder with the passenger side tires on ice and the driver side tires on a dry surface only the passenger side will spin if both differentials are open (non locking). Torque will always go to the drive wheel with the least friction.
Senior Member
Joined: Jan 2020
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From: Somewhere on the south side of Heaven.
Nope. An open differential sends equal torque to both wheels. If one wheel is on ice and the other is on dry pavement, they will get equal torque, which is limited by the wheel on ice ... but they are getting the same torque. If both tires have adequate traction for the total torque available, the spider gears don't rotate on their axes, they just orbit around the axis of the axle shafts.
A locking differential sends torque to each wheel according to the traction available at that tire/road interface. The tire on ice gets very little torque and the one on dry pavement gets almost all the torque provided, assuming it doesn't get too much and slip.
In the end, the open differentials really are driving all four wheels equally, even though you may not like the results.
FYI an e-locking differential like in the F150 actually locks the differential directly so both axles turn together as if there were no differential. You can feel it if you turn it on and drive on dry pavement as the inside axle will usually wind up, then relieve itself when the tire spins, and then wind up again, etc. There are traction control systems on open diffs that use brakes to apply resistance to the wheel that is spinning, increasing the torque used by that wheel, so that the other wheel will also use more torque.
A locking differential sends torque to each wheel according to the traction available at that tire/road interface. The tire on ice gets very little torque and the one on dry pavement gets almost all the torque provided, assuming it doesn't get too much and slip.
In the end, the open differentials really are driving all four wheels equally, even though you may not like the results.
FYI an e-locking differential like in the F150 actually locks the differential directly so both axles turn together as if there were no differential. You can feel it if you turn it on and drive on dry pavement as the inside axle will usually wind up, then relieve itself when the tire spins, and then wind up again, etc. There are traction control systems on open diffs that use brakes to apply resistance to the wheel that is spinning, increasing the torque used by that wheel, so that the other wheel will also use more torque.
Spot on.
Most people have an incorrect opinion about open differentials.
At all times, both wheels get the same amount of power. Absolutely never is power only delivered to one wheel.
With an open diff, if one tire is able to break free, the same amount of power is still being provided to the wheel that isnt spinning. Problem is, that amount of power isnt enough. Traction control makes it harder for the "loose" wheel to spin, increasing the torque required to spin it.
As it becomes harder to spin the loose tire(because TC applies brakes to it), that increase torque is also delivered to the opposite wheel.
Lockers eliminate the ability to differentiate one wheel from the other.
Senior Member
Joined: Jan 2020
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From: Somewhere on the south side of Heaven.
The amount of torque applied to the tire on ice, is also applied to the tire on pavement. That torque is insufficient to move the vehicle. When traction control kicks in, it increases the effort to spin that tire thats on ice. And that increased effort, is also applied to the tire on pavement.
Senior Member
Joined: Jan 2013
Posts: 608
Likes: 314
Traction control makes it harder for the "loose" wheel to spin, increasing the torque required to spin it.
As it becomes harder to spin the loose tire(because TC applies brakes to it), that increase torque is also delivered to the opposite wheel.
Lockers eliminate the ability to differentiate one wheel from the other.
As it becomes harder to spin the loose tire(because TC applies brakes to it), that increase torque is also delivered to the opposite wheel.
Lockers eliminate the ability to differentiate one wheel from the other.
Senior Member
Joined: Jan 2013
Posts: 608
Likes: 314
Pardon my ignorance, the ford build site specifies regular axle and not "open" as well as the window sticker
are we talking about the same type of axles? My understanding of regular is one wheel driven only.
I appreciate everyones knowledge on axles in this thread, didnt mean to start a fist fight over it
are we talking about the same type of axles? My understanding of regular is one wheel driven only.
I appreciate everyones knowledge on axles in this thread, didnt mean to start a fist fight over it
Senior Member
Joined: Apr 2019
Posts: 680
Likes: 446
From: Missouri
The position that an open differential applies torque equally to both wheels at all times, while technically correct from a physics standpoint, is nonsensical in practicality when framed with the "true 4wd" comment. In the icy shoulder scenario the "equal" torque applied is near zero and effectively makes it zero wheel drive. In almost no scenario when 4wd might be needed are open diffs a preferred setup over a limited slip or locking diff.
FORD lifer
Joined: Jul 2011
Posts: 1,239
Likes: 255
From: The Quad Cities - relocated from Montana
True 4WD
Lots of trucks are full 4WD - like my 2011 F150 XLT, with a Eaton TrueTrac in the rear, and the Torsen/Raptor front differential.
I’ve got a zombie thread here about it.
Its not a cheap mod, but it is awesome.
I’ve got a zombie thread here about it.
Its not a cheap mod, but it is awesome.