eLSD question

[pitter_patter]

I'm going to push back a little here. It's true that the terminology has been diluted some, in general, the term "eLSD" typically refers to a limited slip design that is electronically adjustable. By that, I mean LSD hardware that responds to electronic controls. This is done a bunch of different ways, but there is a lot more to it than just the combination of an open diff and traction control.

More often than not, eLSDs have a clutch pack, and the load across the clutch is adjustable. In a few cases, the clutch pack was actually next the differential, but usually it is inside the diff (just like a conventional LSD). 15 years ago, Dana made a design that used a gerotor pump to create hydraulic pressure to compress its clutch. The electronic control was in the form of a bleed valve that allowed it to dump pressure.

Fast forward to now, the current Expedition uses an eLSD with a hydraulic pump mounted outside the axle carrier. The pump pressure is electronically governed, and works a piston on the end of the diff case. An apply plate pushes through the diff case to operate a clutch. I actually just ordered one of these this morning for benchmarking R&D work. There are also designs that use a magnetic coil to operate a ball cam, which operates the clutch. Others still use a motor and sector gear.

The bottom line here is that there are a lot of different versions out there that use actual adjustable hardware, which lets the computer change the locking effect / torque bias ratio of the differential, and do so on the fly, extremely quickly. Top model Corvettes and Camaros have used these to adjust their diff's performance and tweak it to each corner they apex on a track. OTOH, vehicles like Expedition use it to make it more stable in towing and to add to off-road capability while still maintaining good road manners.

With all of that said, Bronco does not use an eLSD in any of these forms (though it will have traction control). Basic axles have open differentials. Some packages/model include eLockers (not to be confused with eLSD), that allow the open to be locked on demand. But no eLSD.

On the Bronco with the eLockers, what is actually happening mechanically when the rear and/or front diff is locked vs. something that has a limited slip diff with lockers?

On the Bronco if the with the diffs "locked" will both tires spin at the exact same rate regardless of traction? Or will the open side only get power if the other tire isn't getting traction?

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[3Dogs]

On the Bronco with the eLockers, what is actually happening mechanically when the rear and/or front diff is locked vs. something that has a limited slip diff with lockers?

On the Bronco if the with the diffs "locked" will both tires spin at the exact same rate regardless of traction? Or will the open side only get power if the other tire isn't getting traction?

Yes.
Locked is locked, and when engaged, both tires will spin at the same rate.

Limited-slip is different. It puts a clutch pack in the differential, allowing some slip, but diverting some torque to the side with traction.

 

[WillisC’onnors]

On the Bronco with the eLockers, what is actually happening mechanically when the rear and/or front diff is locked vs. something that has a limited slip diff with lockers?

On the Bronco if the with the diffs "locked" will both tires spin at the exact same rate regardless of traction? Or will the open side only get power if the other tire isn't getting traction?

https://www.cjponyparts.com/resourc...w both wheels,doing some hardcore off-roading.

 

[pitter_patter]

Yes.
Locked is locked, and when engaged, both tires will spin at the same rate.

Limited-slip is different. It puts a clutch pack in the differential, allowing some slip, but diverting some torque to the side with traction.

Is that because of something mechanical - a pin or ring moving into place - or because the computer is using brakes to add drag to simulate traction.

 

[WillisC’onnors]

On the Bronco with the eLockers, what is actually happening mechanically when the rear and/or front diff is locked vs. something that has a limited slip diff with lockers?

On the Bronco if the with the diffs "locked" will both tires spin at the exact same rate regardless of traction? Or will the open side only get power if the other tire isn't getting traction?

LSD will disengage automatically, E-Lockers need to be turned off. Hopefully this helps a little.

 

[WillisC’onnors]

Here is a pretty good explanation of the 4A system


https://www.roadandtrack.com/car-culture/a12463441/ford-raptor-has-awd-and-4wd/

 

[pitter_patter]

The Bronco has open differentials, so I'm trying to figure out what the eLocker is actually "locking." You're pointing me to LSD information.

i.e. are the eLockers just simulating a locking diff? and if so, how?

LSD will disengage automatically, E-Lockers need to be turned off. Hopefully this helps a little.

Here is a pretty good explanation of the 4A system


https://www.roadandtrack.com/car-culture/a12463441/ford-raptor-has-awd-and-4wd/

 

[pitter_patter]

If this is what the Bronco is running then, this answers my question.

https://www.cjponyparts.com/resources/locking-differentials-explained#:~:text=Locking differentials allow both wheels,doing some hardcore off-roading.

 

[pozi240]

I thought this information was well known on here by now (I know its known, since there is some good info in this thread now), but, the rear locker used in my 2020 Ranger FX4 is a new technology Dana AdvanTEK M220 (Dana 44). It is a mechanical locking rear end with electronic control. This will be the same rear differential used in the new Bronco as well (with different gearing options of course). It also the same design as the optional rear end in the Jeep JL Rubicon as well. (the front axel in my Ranger is the Dana AdvanTEK M210 (Dana 40). I can assure you after owning and driving this Ranger for a few months now, that in "unlocked" mode, it behaves very much like a typical LSD but not quite as much "lock up", but, it is certainly not a fully "open" diff as well. When you lock this rear end with the switch, it is like the old "Detroit Lockers" from back in the day on the drag strip. You better be going straight and not turning on dry pavement.....LOL.... your driveline and tires will hate you. https://spicerparts.com/parts/axle/automotive/advantek-axle-technology

 

[Laminar]

I can assure you after owning and driving this Ranger for a few months now, that in "unlocked" mode, it behaves very much like a typical LSD but not quite as much "lock up", but, it is certainly not a fully "open" diff as well.

I can find no indication that there is any type of mechanical or clutch-based solution in addition to the locker. What causes it to act like a typical LSD?

 

[Laminar]

The Bronco has open differentials, so I'm trying to figure out what the eLocker is actually "locking." You're pointing me to LSD information.

i.e. are the eLockers just simulating a locking diff? and if so, how?

The Bronco's E-Locker IS a locking diff. The lock is actuated by an electric mechanism. When active, the rear wheels are mechanically tied together and will both spin at exactly the same rate no matter where traction lies.

 

[pozi240]

I can find no indication that there is any type of mechanical or clutch-based solution in addition to the locker. What causes it to act like a typical LSD?

It will spin both tires when I experience traction loss (behaves like the Dana in my Mustang GT), however, if I have one wheel on ice/snow and Traction control is fully disabled, it behaves more like an "open diff"

 

[Laminar]

Ford said on bronco sport documents that a sport could sent 100% of power to one wheel.... Meaning it's using hardcore ABS "lockers".......

It's not. The Sport is utilizing the GKN Twinster system, same as the Focus RS, Land Rover Evoque, Lincoln MKZ, and others. The rear diff isn't a diff at all, just a straight ring and pinion. Then each axle coming off of the diff has a clutch pack. The computer can modulate power going to each rear wheel, and it can fully lock the wheels together if it wants to.

On the Focus, the rear wheels are actually geared to be overdriven compared to the front. So if the rear axles are locked up, the rear wheels are spinning faster than the front AKA Drift Mode.

 

[Laminar]

It will spin both tires when I experience traction loss (behaves like the Dana in my Mustang GT), however, if I have one wheel on ice/snow and Traction control is fully disabled, it behaves more like an "open diff"

Yeah, that's how every open diff acts today. Nothing inside the diff is helping both wheels spin like a real LSD would do.

 

[pozi240]

Yeah, that's how every open diff acts today. Nothing inside the diff is helping both wheels spin like a real LSD would do.

I understand that, however, an open diff should not be able to leave "two black strips" on dry pavement, correct? (like the LSD in my Mustang does)..... (side note: the Ranger does and that is without the locker engaged)... confusing, right?

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