Automatic switch for uncoupling front wheel drive - uses switch linked to higher gear settings in four wheel drive transmissions

摘要

The front wheel drive is switched on by an electro-magnetic valve operating on a hydraulic servo line. The control line to the valve is fitted with a manual selector switch so that the driver can select four wheel drive. The gear lever into the main gear box is linked to a second switch which blocks the line to the electro-magnetic valve when the gear lever is moved into the higher gears. The high-low ratio control gear lever is likewise fitted with a switch in the control line so that the line is blocked when a high ratio is selected. The fail-safe system prevents the four wheel drive being engaged when the vehicle is operating at higher speeds, in which condition the drive can be damaged.