Interesting post. What I don't understand is back when I had 2000 year pickup with limited slip, I didn't have to activate it electronically with a switch on the dash, it also had no braking involved for the wheel that loses traction first. To me this is better if I am in hurry I want no braking, if one wheel starts to spin the limited slip should work automatically like they use to. To me the current state seems like a regression rather than an advance in technology, capability.

 

I don’t understand why you feel like you need limited slip with the electronic e-locker. The system also uses the brakes to control wheel spin when in 2H.

 

Right, but let’s not confuse electronic locking with limited slip. All limited slip setups I’m aware of are passive in that they don’t require any user interaction.

To answer your question, there are two reasons that I can think of why Ford uses the brake-based approach over a traditional limited skip differential:

1) Cost. Software is expensive upfront, but cheap over millions of trucks. To program existing hardware for double duty is cheaper than installing hardware into every unit sold.
2) Efficiency. There is an efficiency penalty in terms of additional driveline losses with limited slip setups as compared to an open differential.

 

As mentioned, limited slip and the e-locker are not the same.

I prefer the locker. Limited slip differentials with clutches wear out. Once the clutches burn up its as good as an open differential.
The e-locker performs far better for as intended usage. In situations such as boat ramps or off roading a locker is far better. As for on road, trucks with working limited slips will fish tail in the snow a lot easier than trucks with open differentials. So safety might be a factor.

GM trucks offer a auto-locker that engages when there is enough of a difference in tire speed. It is better than no locker but its engagement can be kind of harsh. In off road or boat ramps its not as good as an e-locker because a tire has to already lose traction for it to work.

I use my e-locker in mild off roading for hunting. And in the snow I have used it to get up hills.

 

I don't I was just curious why the limited slip which was automatic was replaced by the manually activated electronic e-locker.

 

I'll take a shot at this. LS differentials are always in use, even when they are detrimental, EL are positive on/off. LS use special gear lube in most circumstances, EL use common fluid. LS can wear out, EL does not wear. KM

 

3) Better vehicle stability at speed in slippery conditions.
4.) Better braking control of rear wheels individually.

These two are among the reasons the auto locker is disabled above 25 mph.

 

The torque to the wheel on dry pavement is equal to the torque on the side spinning on ice. The side on dry will receive the minimal torque the spinning tire is able to create due to the tire/ice interface, plus torque due to friction (bearings, oil drag, etc.) plus the inertial resistance of accelerating the wheel (which is transient). Torque doesn't require motion, so it's there on the dry side, it just isn't enough to move the vehicle.

There is no torque limiting TO the spinning wheel other than what the engine and transmission can create, but the most torque that will be applied to either side is as described above.

It's been a long time since physics class so likely my terminology isn't quite on-point.

 

There is more to this that in not being addressed.
A. the Rear electric lock feature, if you have a need for it.
B. When locked in 2H or 4H,, the Pcm control will unlock it above 25 mph and relock at 20 mph.
C. In 4 Low, lock it will stay locked up. You want this feature for off road-ing as wheel scuffing is usually on soft surfaces and much less. You don't want a wheel hanging in the air spinning in an of road crawl.
D There is a reason for these actions.
1. no lock up at higher speeds are safe in 2wd or 4H mode and would only reduce vehicle control and cause excessive wear on tires and the drive line.
2. for those who go off road crawling in 4 Low, you would not want the rear to unlock once you initiated it or you won't go very far.
3. in Wet/Snow driving mode, the ABS Brake system will control the rear traction. Notice I did not say lockup. And the throttle response is reduced in the name of traction to reduce throttle sensitivity and help traction.
It apples braking action to the the wheel with the lest traction and forces torque to the side with the most traction at any moment and driver transparency.
Believe, it work very well.
4. As many possible combinations as one would need to a pickup.
Remember there are competitors out there that would not purchase, if the truck did not have the above features.
Good luck.

 

Your first sentence contradicts the second sentence.
Is it equal or minimal?

My point is once one side loses traction it gets all the torque except for parasitic drag inside the case. A locked rear always equally splits power between each side therefore no spin and forward movement. The claim of equal power to both sides in an open differential is wrong, otherwise you wouldnt need a locker.

Its called an open rear because its fully controlled by varying outside forces, not internal clutches or a locking mechanism.

Your second paragraph, the engine and trans creates and delivers torque, it has no control over the actual operation of the differential. Torque delivery to each side is random, controlled by friction between the tire and ground or by the brake, if engaged on one side.