OPEN DIFFERENTIAL - allows your tires to spin at different speeds which is important if you want to turn a corner.
Torque goes to the wheel with the LEAST amount of traction, and the other wheel gets the same amount of torque. Thus, if you are spinning the left wheel, there is very little torque, and the same very little torque goes to the right wheel.
ESC (electronic stability control) and BLD (brake lock differential, which other brands like Toyota call traction control) are slightly different.
ESC is an amazing safety device for normal driving. It controls individual brake to each wheel AND it controls the throttle to keep you from sliding around. It really saves lives on wet roads which is why it's been mandatory for several years.
ESC can be turned off with a button as mentioned above.
Dropping into 4lo will also turn off ESC.
BLD stays on ALL THE TIME. BLD uses just the brake to control wheel spin. It will apply brake force to the spinning wheel, which allows the other wheel to get some torque = brake force.
OPEN DIFF EXAMPLE
1 wheel in the air or on ice, zero traction. This wheel spins with essentially zero torque. An open diff forces the same torque to each wheel, so the other wheel also has essentially zero torque.
without an LSD, the BLD applies brake force to the slipping wheel. Let's say It takes 10 ft lbs of torque to stop the wheel spin. The other wheel gets some 10 ftlbs of engine torque = the brake force. And if 10 ft lbs is enough to get you going, you move. If not, you don't.
One reason PIPI (and the Renegade) did pretty well in the rocks is because they have BLD.
LSD EXAMPLE - limited slip differential or positraction
1 wheel in the air or on ice, zero traction. This wheel spins with essentially zero torque.
The LSD has a bias factor, let's say 3;1. So the other wheel gets 3x0 or still zero torque.
Which is why people tell you that an LSD isn't any good when you have a wheel in the air.
But wait, there's more.
BLD notices the wheel is spinning and applies brake force - assume the same 10 ft lbs.
Because you have an LSD, the bias will apply 3x = 30 ft lbs to the other wheel. Normally this is enough to get you moving.
AKA, 3 times as much torque as you got from BLD alone.
BOTTOM LINE
LSD and BSD work very well together.
Technical explanation of LSD vs Open
Living With Limited Slip Differentials (motortrend.com)
5 Benefits of a Limited Slip Differential (How It Works and Its Cons) (oards.com)
Good discussion on LSD
(5) Jeep & Limited Slip Differential Types | Jeep Wrangler Forum
BEACH SAND TEST OF TRACTION CONTROLS | Tacoma World
- note I think A-Trac is the word Toyota used for the same system Jeep calls BLD.
ESC will save your life and the lives of others on the roadway in slick conditions. It has been well proven, which is why it is mandatory on USA cars starting in 2011.
And you also have a button so you can manually disable it when the situation calls for it.
And the Jeep systems engineers turn it off in 4lo because by definition you should never been in 4lo on a normal roadway which is when you need traction control.
4hi on the other hand is often used for slick road driving so traction control is automatically engaged - and you can turn it off if needed. But each time your restart the car the reason the system will turn it back on is for the safety of others - and yourself.