Here's how it works:
1. Transfer Case: The transfer case sits between the transmission and the front and rear driveshafts. It has different positions, typically including 2WD (2-wheel drive), 4WD (4-wheel drive, often called "high"), and 4WD Low (4-wheel drive low range).
2. Automatic Locking Hubs: Integrated into the front wheel hubs themselves are mechanisms that automatically engage. When the transfer case is shifted into 4WD (high or low), the front drive shafts begin to rotate. This rotation activates the automatic hubs, effectively locking the front axle to the rotating drive shafts. The hubs use a vacuum-controlled system or a more sophisticated electronic system (depending on the specific model year/trim) to engage. This means there's no need for manual engagement of the hubs themselves.
3. Disengagement: When the transfer case is shifted back to 2WD, the front drive shafts stop rotating. This causes the automatic hubs to disengage, allowing the front wheels to freely spin without being driven.
Essentially, the automatic locking hubs act as a clutch, automatically connecting the front axles to the drive train only when 4WD is engaged. They simplify the 4WD operation by eliminating the need for manual hub locking, but they do rely on the vacuum or electronic system to operate correctly. If this system fails, the front wheels may not engage in 4WD.
