Viscous Coupling.

This is a viscous coupling as found attached to the centre diff' in the transfer case of a Range Rover. It has been cut away to reveal the internal plates. These are alternately keyed to the casing or the centre shaft. Normally a viscous fluid fills the casing and this resists strongly large differences in rotational speed between the plates, ie. it resists the front and rear transfer-case output shafts rotating at very different rates. In this role it limits wheel spin if a front (or a rear) wheel suddenly looses traction. The action is smooth and permits normal differential action when cornering.

The viscous coupling does not help if both a front and a rear wheel loose traction as the Range Rover does not have axle diff' locks (as standard).

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