HYDRAULIC AWD

The folks at Tuthill are no strangers to hydraulics, and their very specialized EZ Trac all-wheel-drive system is based on simple hydraulic technology, versus a complicated drive-shaft-and-transfer-case arrangement. As the maker says, it allows users to go from highway to “hardway” with the flick of a switch. It’s retrofittable.

It’s actually a standard production offering on some MAN trucks in Europe, where it’s called ‘HydroDrive’. There are more than 5000 units in operation in all.

Typical applications are 12,000- to 20,000-lb axles for: aerial bucket trucks, tow trucks, concrete pumpers, refuse trucks, and emergency vehicles, among others.

What you get is a hydraulically driven steer axle that maintains OEM ride height, ride comfort, and turning radius — plus on-demand additional traction. In manual mode, the driver can switch the system on when he’s gone off-road and then on when returning to pavement for high-speed freewheeling. In automatic mode, system software senses rear-wheel slip, engages AWD and then disengages it at 20 mph and above. The system can be engaged or disengaged on the fly below that speed. There are no highway speed limitations when disengaged, and with no gears in the system, there’s no windage loss.

System components include a clutch, pump, valve, electronic controller, electric fan, auxiliary charge pump, plus oil cooler, reservoir and filtration.

Benefits include about 800 lb less weight compared to drive-shaft-and-transfer-case systems, the maker claims, which equals lower fuel consumption — Tuthill estimates a 10% saving. Also pretty useful is the lower center of gravity, which means the truck is less likely to roll over on hill sides. As well, the truck is lower so you get easier cab access.
 
Installation time is projected at 30 man-hours, says Tuthill.


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