1999 Toyota 4Runner 4+4

Hello don marchand

Welcome to 2carpros

Mud, rust or worn parts inside the hub can prevent the mechanism from sliding in and locking the hub
To check engagement, rotate the axle shaft backwards. This should lock the hub. Try turning the wheel by hand again. The axle shaft should now turn with the wheel if the hub is locked. If the hub fails to lock, the hub will have to be disassembled and inspected or replaced
To check release, hold the axle shaft steady and rotate the wheel backwards. You should hear a click as the locking mechanism slides back out and disengages the hub. Rotate the wheel forward again and it should turn freely.