Chevy/GMC K-Series. 1500, 2500, 3500 Pickup, Suburban, Tahoe, Yukon. 4x4 Posi-Lok replaces the thermal linear actuator with a cable operated actuator that puts the driver in control of the engagement from inside the cab. After engaging the transfer case, a one Perfect Steerable Transfer Carth pull of the 4x4 Posi-Lok cable slides the shift fork and collar to connect the