Viscous Coupling: Testing and Inspection

VISCOUS UNIT (Front output housing)

In Vehicle Check
The viscous unit is located in the front output housing. its operation can be checked while the unit is installed in the transfer case as follows.

Remove either the front or rear drive shaft from the vehicle to eliminate drive to one of the axles. If the viscous unit is operating effectively drive will be transferred to the axle that is still connected via the drive shaft to the gearbox and the vehicle should remain driveable.

If the viscous unit has failed, drive will not be transmitted to the axle.

A partially failed unit will be identified by excessively high engine revs and little vehicle movement when attempting to drive the vehicle.