4WD MODIFICATIONS - GENERAL MODS
Bob James’ 6×6 Australia has been working on 4×4 modifications since 1984 and now does many 6×6 conversions on popular 4×4 utes and wagons, plus some 4×4 light trucks.
Outback Travel Australia’s Allan Whiting was trained by Volvo Trucks as a military vehicle specialist (many years ago, he points out) and therefore has a particular interest in high-mobility off-road vehicles.
While demonstrating the Volvo C3 4×4 and 6×6 vehicles to the Australian Army, he also had the opportunity to drive the Steyr-Puch Pinzgauer 6×6 as well. There’s no doubt in his mind that a compact 6×6 is hard to beat in the go-anywhere stakes.
The Mercedes-Benz G-Wagon is the only factory 6×6 in Australia
Unfortunately, the demand for such a vehicle is limited – often by the depth of people’s pockets – so there’s nothing off-the-shelf in the market, other than military vehicles. OTA understands that Mercedes-Benz Australia planned to sell the G-Wagon 6×6 that it developed for the Australian Army, but was not allowed to do so, under the terms of the Army purchase contract.
Allan Whiting did get to drive one of the Australian Army G-Wagon 6×6 development vehicles and was suitably impressed by its off-road ability, if not by its appalling on-road, in-cabin noise level.
For those contemplating a 6×6 vehicle as the base for a go-anywhere travel machine, the process involves buying a suitable 4×4 and having it converted to 6×6. There are several companies doing this work, but 6×6 Australia is one of the longest-serving and has come up with one of the best rear-tandem-axle designs.
Since 1996, 6×6 Australia has been supplying the only 50:50 load-share, coil spring, tandem-bogie suspension in the after-market. It was designed by Bob James to offer superlative wheel travel for off-road work and with an inherent ‘roll-steer’ function for optimal on-road handling.
The key components of the wheel-travel design are two centrally-pivoting beams and four coil springs. The beams act like see-saws, letting the axles rise and fall over uneven terrain, while the coils give smooth, maximum suspension travel. Spring reaction is controlled by dampers at all four corners.
6×6 Australia’s inter-axle beams
Axle acceleration and braking torque reaction in the axles is absorbed by lower trailing and leading arms, and upper A-arms that pivot from above the centre trunnion cross member, so that the arms and the beams work in concert, with compatible arcs of travel. The A-arms also control lateral axle movement, so there’s no need for Panhard rods.
6×6 Australia’s axle-locating arm layout
A bonus of the bogie design is inbuilt ‘roll steer’. When the vehicle is cornering the outer-radius coil springs compress more than the inners and this action slightly extends the bogie wheelbase of the outside wheels and slightly reduces the bogie wheelbase on the inner wheels. This inherent bogie ‘steering’ minimises bogie ‘drag’ when cornering – a condition with which truck drivers are all too familiar.
6×6 Australia’s through-drive pinion shaft and power divider
Bogie ‘drag’ is also minimised by 6×6 Australia’s power-divider design. The leading rear axle is through-drilled and houses a special pinion shaft. The shaft passes through the back of the axle housing to a universal joint that mates with a jack shaft that drives the rear (third) axle. But between the through-shaft and the uni-joint is a power divider that is normally unlocked, so that the third axle is non-driven and just free-wheels. That’s good for reduced ‘drag’, less tyre wear and better fuel consumption.
However, the 6×6 Australia conversion is a true ‘6×6’, so when there’s any slip detected – a difference in shaft speed between the two bogie axles – the power divider intervenes automatically and varies drive torque between the two axles to suit the grip conditions. That state can vary from 100-percent to the front or to the rear bogie axle and any shared percentage between both of them. That happens automatically, without driver intervention.
Chassis extension, rebuild and central suspension trunnion mount
Of course, GVM upgrades are an important part of every conversion and 6×6 Australia can offer approved GVMs up to 8000kg. The company is currently working on the gap between 8000kg and 15,000kg in the light-truck arena.
6×6 Australia received its first Federal Identity Plate Approval in 1998 and now has many approvals for different makes and models. The price for a 6×6+GVM-upgrade conversion starts at around 60 grand, plus GST and takes between six and eight weeks. Bodywork and accessories fitment is optiionally extra.