Seriously, just stop it. The statement was always wrong and the folks over at team O’Neil Racing decided to put it on video to show the difference in stopping distance between 2WD and 4WD.
Jeep Vs Jeep
Two Jeep Cherokee XJ’s on the same tires going head to head. To make sure it was accurate both ran in 2wd and both did it in 4WD. The vehicle with 4WD engaged stopped shorter every single time.
You can see in the video that the rear wheels do not lock up. There isn’t enough friction from the surface to overcome the power the engine delivers even at idle. Couple that with the momentum of the vehicle and you can see the results. Those of us who grew up driving in the snow with only 2WD vehicles learned early on to put the transmission in neutral or push the clutch in to prevent this. Many modern vehicles don’t allow this easily, so the technique is falling by the wayside. Even with that, the additional traction that the 4WD system provides is beneficial, just not as much.
In 4WD, the center differential locks up, linking all the wheels together. This prevents the rear wheels from spinning. The front wheels are slowing down, which slows down the driveshaft, which then slows down the rear wheels. That process results in less wheel spinning in the rear maximizes the available traction shortening your braking distance. This effect happens regardless of the type of slippery surface. No, it won’t miraculously save you on ice but it will give you a better chance of finding any available traction.
Don’t take this advice and use it to drive like a moron. Keep it in your skill set to help you avoid an accident, make it home safely, and so you don’t wreck into me.