Ina 4x4 GROUP TEST
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• One of the lighter 4x4s in the test, the Cargo demonstrated what big manufacturer money can do for a chassis. It features permanent fourwheel drive with a 67/33% front/rear split. There are 12 forward speeds (six normal and six low range) as well as a neutral position designed for PTO operation.
Go-anywhere ability gets a big boost from inter-axle diff-locks, a centre locking diff and cross-axle locks front and rear. The front lock features a warning buzzer to remind of the restricted steering when it is engaged. All locks can be engaged if the road speed is below 10km/h; the whole lot is controlled by three pneumatic controls behind the gearlever.
Additional ground clearance is achieved by mounting the standard Cargo cab 100mm higher on the chassis; the bottom cab step flips up to avoid damage.
In the rough the Cargo stood out from the crowd with by far the best ride. Roll was well contained for a chassis with a high centre-of-gravity. Combined with outstanding refinement, hill climbing ability and an excellent exhaust brake, the Cargo really made a good case for itself. It might lack the ultimate goanywhere abilities of the Unitnog, but that's not the point in this class. For mainly on-road use the Cargo is hard to beat (despite its 6.95:1 diff ratio limiting top speed) while its off-road capabilities and good manners were better than we expected from any of the vehicles we tested. On balance, this is the best of the bunch.
• Mercedes-Benz offers a comprehensive range of all-wheel-drive vehicles. In the 17tonne class its contender is the 1820AK; the more sophisticated Unimog range caters for the lighter end of this sector.
The 4x4 1820AK shares its chassis and cab height with the 4x2 1820K tipper model, which was designed for increased ground clearance in the first place.
It also shares its engine with other Mercedes 1820 models, but any similarity between their drivelines ends there. Driving through a six-speed gearbox, the AK has permanent four-wheel drive. The central transfer box offers high and low ratios giving 12 speeds in all. It also features an inter-axle difflock, while both front and rear axles are fitted
with crosslocks. All difflocks can be engaged at any speed as long as no wheels are spinning. Operation is by
rotary air valves behind the gear lever. While the Mercedes is not over-endowed with power when compared with the lighter models in our test group, well-chosen gear ratios ensure that its performance is up to the job.
A greater surprise was the ride quality. The Mercedes cab has two-point coil suspension at the rear and rubber bushes on the cab pivots at the front with a fixed driver's seat. Several other vehicles in the test could boast more sophisticated suspension, but few could better the 1820's ride.
Mercedes even makes a distinction between gritter and tipper chassis: the gritter gets slightly slower gearing, a heated front screen and a centre seat.