The Defender Four Wheel Steer

The 130 of Patrice Ryder/Outback Import

This is about the Australian company Maxi-Drive Engineering (MDE) who make a steering axle for Land Rovers. The following text is largely from them, just shortened a bit. The units main drawback is the price- I believe it runs around 10.000 US$! Boy, my last Defender was less expensive than that!

Due to higher axle loading on the rear axle it is NOT a simple matter of putting a front axle in the back.

The original Salisbury SHA differential (although also fitted with a Maxi-Drive lockable diff) is retained. The tubes are shortened and fitted with new flanges to accept the swivel assemblies. The swivel housings are Series 3 but the hard chromed swivel balls are made by Maxi-Drive. Those are made of 4140 Chrome Moly steel and with slimmer swivel bearings offer sufficient internal clearance to accept constant velocity joints from the 101 FC. Those super strong units were chosen as the standard CV's were not adequate for the rear axle fitted with a diff lock.New stub axles (spindles) are also machined of 4340 chrome nickle steel to accept the larger diametre outer axle.. The original Defender hubs are fitted witch also retain the original discs but use Range Rover front calipers. An MDE special drive flange with screw-on caps connects CV to hub. Also MDE axles are used to connect diff to CV. Special steering levers to provide higher strenght and a higher mounted track rod are manufactured from Bisalloy 80 high tensile plate.The track rod is basically a standard MDE heavy duty track rod of special lenght.

The steering is totally actuated hydraulically. A simple MDE compact hydraulic ram is fitted directly on to the diff, the fixed end being attached to a stenghtened diff hat. The shaft being atteched via a rubber bush to the track rod. Hydraulic pressue is supplied ba a commercially available 12V hydraulic compressor similar to those used on tippers etc. A control joy stick operates a standard 2-way control valve with an incorporated interlock unit. This mechanically inhibits usage of the rear wheel steering when the transfer case is not in low range.

The system is actuated by a self-centering joystick near the middle console

The most unique component is the self centering lock unit (SCLU). This is made by MDE and looks like another hydraulic ram with a vacuum actuator on one side. It's funtion is to provide precise centering of the rear wheels with zero float without the need for an hydraulic location. The SLCU is vital for driving on highways. It insures the car does not behave in other ways than a standard Land Rover. Also the actuator rod is hydraulically locked when in high range.

The rear steering beeing independant of the front allows the driver to steer the rear where ever nad when ever chosen.This allows the vehicle to traverse side ways if the front and rear are angled the same or a minimum of 9 metres turning circle if wheels angled opposite.

The hydraulic pump only operates on demand, the signal being provided by the control joystick. Warning lights indicate when the SLCU is open and if primary power is switched on.

Specifications

Differential 8HA Salisbury (original)
Inner axles MDE
Swivel balls MDE
Swivel housings Land Rover Series 3
Stub axles MDE
Hubs Defender original
Drive flanges MDE
Discs Defender original
Calipers Range Rover front
Steering levers MDE
Track rod MDE
Track Rod Ends Defender
Main Ram MDE
Central locking unit MDE
Hydraulic power pack 12V portable power unit
Speed from lock to lock 3 seconds
Max steering lock 30°
Crabbing angle 30°
Minimum turning circle 9 metres

Important own comment: The system DOES work. I've seen it myself and it looks very professional. It was designed for the Australian Outback and it survided the test. Wish I could afford one.

I still haven't found MDE on The Net, if you find them please e-mail me. For other questions write to Outback Import who imports the kit into France and the rest of Europe.