Locking rear axle is open differential when not locked?

[v8440]

Hi all,

Got an axle question here. If I end up buying a rcsb 4x4 f150 I will get an e locker axle by default-no other option. Will this thing automatically lock if tire spin happens, or will it sit there and let you blaze the right tire forever? I'm hoping it's automatic and competent at it, an open rear end with a whipple (which I plan to get if I get a truck) is just dumb. I've seen conflicting reports on the internets when I searched.

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[Gros Ventre]

Yes, its an open differential when not locked. Whether the right or left rear wheel spins depends on which one has the least traction (ie the wheel with the least traction gets the most torque/power applied). The wheel with the most traction won't move. Lock it and both move together, so plan ahead.

 

[Big Dog Daddy]

Yes, it's an open differential when the locker is not in use.

 

[v8440]

The wheels get equal torque with an open rearend with no regard to wheel speed. The one with the least traction therefore spins, and that one is generally the right side in normal acceleration because the torque reaction to driveshaft rotation tries to pick up the right side rear tire and plant the left. That's why vehicles tend to "torque over" to the right-they're not putting more weight on the right side like it appears, they're actually putting less on that side. In any case, thanks for letting me know they're not automatic. It's kind of a shame, with all the computer power these things have I think engaging the locker just before or right as wheel spin starts would be possible.

 

[Buyer2021]

I'm hoping it's automatic....

Well, not exactly 100%, it depends on the selected drive mode ....

The attached may be of interest, describes in detail the operation of the E-locker differential (ELD). The ELD operation is the same for both 8.8 and 9.75 ring gears, semi-floating and 3/4-floating axles.

As you read this, note that with the XL trim you will have the ESOF 4WD system, not the TOD (TOD is only on Lariat and higher trims).

May not describe what you would like, but it is what it is, hope the explanation helps.

 

[v8440]

Thank you sir.

 

[Buyer2021]

So, as you see on the ELD Engagement/Disengagement Speeds and Availability table in that section from the Workshop Manual, ELD does not 'automatically engage' when in Normal. Eco, Sport, Slippery, or Tow/Haul modes.

IF manually engaged below 20MPH in any of those drive modes it will automatically disengage when you cross the 25MPH automatic disengagement speed threshold and will automatically re-engage when you slow to 20MPH.

IIRC you will have to re-select drive modes and ELD engagement if you turn the key off.

 

[FORDTEXAS]

closest thing to an “automatic” is a limited slip differential.

 

[v8440]

closest thing to an “automatic” is a limited slip differential.

True, but since I knew it was a locking differential rather than a limited slip... My '98 dodge dually has an auto locker in it. It will gladly pull a trailer up a hill with one side on pavement and the other in slick mud.

 

[ks54703]

Hi all,

Got an axle question here. If I end up buying a rcsb 4x4 f150 I will get an e locker axle by default-no other option. Will this thing automatically lock if tire spin happens, or will it sit there and let you blaze the right tire forever? I'm hoping it's automatic and competent at it, an open rear end with a whipple (which I plan to get if I get a truck) is just dumb. I've seen conflicting reports on the internets when I searched.

Your E-locker only locks if you engage it with the center button in the drive mode selector and it will then show up on the screen, Can be locked in both 2 wheel and 4 wheel drive and only recommended to do so on loose or slippery surfaces. It also will auto disengage at speeds over 20mph.

The kicker is today's traction control will slow the spinning wheel thus the wheel with the most traction will have more torque applied to it. Same is true while in 4 wheel drive.

Turn off the traction control with 2 pushes find a safe area with a loose surface area and go balls to the walls and only 1 rear wheel will spin. Engage your E-locker and retry now both rear wheels will spin.

 

[Jeff1779]

I have a 21 lariat PB. It has the locking diff. It seems most of the time for me it’s a limited slip. Locking with the button is definitely a full lock. It will chatter the tires in a tight turn like an old race car with a spool locked rear end.

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