Disclosed is a four-wheel-drive all terrain vehicle capable of smoothly
braking wheels in braking operation of rear wheels and having simplified structures
of a drive force disconnecting device and a 2WD/4WD switching device. The drive
force disconnecting device is provided in a power transmission path for front-wheel-drive,
for engagement/disengagement between a cam shaft and an outer race by means of
a torque transmission member such as rollers, to allow a driven-side rotary member
such as the outer race to become free when a drive-side rotary member such as the
cam shaft is braked during 4WD. The rollers are provided between a plurality of
cam faces formed on the cam shaft and a cylindrical friction face formed on the
outer race, and they are placed in a torque transmission state (4WD) in which the
rollers are pressed between the cam faces and the cylindrical friction face or
a torque transmission release state in which the rollers are not pressed between them.
