I have a 2001 Super Crew with 4x4. I've had 4x4's all of my driving life, and am familiar with the old style with the locking hubs and manual transfer case. I also have a 2000 Superduty 4x4 and I understand how the ESOF works on that (vacuum operated front hubs).

Can someone explain how the ESOF on the 1/2 ton work? I noticed that there are no vacuum lines running to the front hubs like there are on my Super Duty, so am I correct in assuming that the front axle shafts rotate all of the time? When you flip the ESOF switch the electric motor engages the transfer case. There is a vacuum operated lever on the front axle, what does it do?

Thanks for the education