BUYERS GUIDE - HEAVY DUTY
Japanese 4×4 light trucks dominate this category, but their shortcomings leave pace for niche marketers, including the once-troubled OKA Motor Company. As of mid-2020 a new Australian-owned OKA All terrain Vehicles organisation has given this marque much-needed revitalisation.
At OTA, we were involved with the OKA project from 1993. At that stage, the Perth-based company was courting customers in the mining and recreation businesses, as well as seeking finance from various sectors, both here and overseas.
Along with the late Ian Glover, OTA’s Allan Whiting was asked to evaluate the OKA prototype and suggest improvements. The original machine had a small cab and we judged the payload insufficient.
At a conference in Sydney following our test drive, then OKA managing director, Mike Walker, confirmed that our criticisms echoed those already made by several mining companies and would be taken into account when the production vehicle was designed.
“All we need now is a good name for the truck,” said Mike Walker. After some thought, Allan Whiting ventured: “You can’t get more Aussie than ‘Okker’, so why don’t you call it that?” The idea resonated, but the spelling was made more professional!
The 2021 OKA
The current vehicle uses the same production cab that was used on all previous OKAs. In standard form it meets mining requirements for roll-over-protection (ROPS – AS1636-1984) and can be specified for falling-object protection (FOPS) if required.
Nice bush-compatible touches are hinged headlight mesh covers and vertically-stacked lights with easily-adjusted beam height.
The cab is formed from zinc-coated flat metal sheets, welded and glued over RHS tube frames, so repairs are low-cost. Also, all glass is flat-panel. The cab is isolation-bolted to the frame, helping front-end stiffness, but that design means there’s no tilt-cab function. However, engine access is via a large lift-up panel between the front seats.
Also carrying over are the stiff, parallel-rail chassis and long, supple leaf springs and this approach is at variance from the Japanese concept of a flexible frame and stiff suspension. In addition to providing a good ride quality the OKA approach also makes it simpler to fit rigid bodywork, such as water tanks, without the need for complex three-point mountings.
Although the proved concept has been retained, in-service experience has led new OKA boss, Dean Robinson and his team to upgrade the powertrain, the axles and the brakes.
In this era of throwaway mentality it’s very refreshing to note that OKA has a refurbishing service for owners of existing vehicles. The rebuild process has its own series designation – ‘R’ – and usually involves replacement engine, transmission, transfer case and axles.
Having driven the original production vehicles we can understand why many owners would want a replacement powertrain, because we were highly critical of the choice of a four-cylinder Perkins Phaser, with only 106hp (79kW) and 354Nm, to haul a GVM of 5500kg. The popular replacement engine by the new OKA organisation is a Cummins 6BT mechanical-injection engine, with outputs of up to 160kW and 600Nm.
The new-build OKA range is designated ‘NT’ and consists of single-cab, dual-cab and multi-cab pick-ups, plus a van body that can be specified for load-carrying, bus seating or pop-top campervan vocations.
All standard models are built on a common, 3190mm wheelbase, with 1664mm track front and rear. GVMs vary from 6500kg to 7100kg and payloads range from 1650kg to 2200kg, depending on body type and options. All variants can pull a 4500kg trailer.
The standard engine for 2021 OKAs is a Cummins ISBe5 (Euro 5) 4.5-litre, four-cylinder, common-rail-injection. It’s available in several stages of tune from Cummins, but OKA has opted for the 136kW/700Nm setting.
The ISBe5 has selective catalytic reduction (SCR) exhaust after-treatment that relies on AdBlue urea dosing, fed from a large, 43-litre tank. AdBlue is readily available all across Australia these days, because most new heavy trucks need it.
The original transmission was a Spicer T5-290 five-speed, connected to an NP205 New Process transfer case, but the 2021 models score a much heavier-rated Tremec TR4050 five-speed and an Allison 1000 Series torque converter, automatic six-speed is optional. The new transfer case is a BAE HD150 variant that’s built specifically for OKA, using proved defence-product engineering. (BAE is internationally recognised for its off-road componentry.)
The 2021-model axles are also modified BAE parts and OKA is in the process of moving to Dana 130 axle centres. Central tire inflation (CTIS) is optional on OKA’s new axles. Standard wheels are steel disc 19.5-inch tubeless and that wheel size is a popular medium-truck fitment.
Original OKAs had four-wheel disc brakes, with vacuum-hydraulic actuation, but the new range has air/hydraulic braking, with air supply from an engine-driven compressor. That compressor can also operate the optional CTIS.
The options list is extensive, including cruise control; winches; differential locks; different wheels and tyres, including beadlocks and an additional fuel tank.
Our assessment of the upgraded OKA is that it’s a greatly improved package, with significant performance and braking benefits over its predecessors. It’s also pleasing to see a company that’s prepared to upgrade pre-loved machines, rather than expecting people to buy new.
On the subject of ‘buy’ it’s important to note that all this custom building and performance doesn’t come cheaply: a typical crew-cab pick-up is around the $190,000 mark and a van body, about 10 grand more.
On and off road
We haven’t been able to drive one of the 2021 models, but given that the cab, chassis, suspension and dimensions are unchanged, we expect its off-road ability to be at least as good as its predecessors. Here is our off-road experience with the original model.
‘Being purpose-built the OKA had impressive off-road dimensions, with a 3.2-metre wheelbase inside overall length of only 5.3 metres resulting in approach and departure angles of 41 degrees, and a belly angle of 150 degrees when loaded.
‘Suspension travel – left wheel bump and right wheel rebound – was 359mm front and 488mm rear.
‘Vision was very good, thanks to the OKA’s forward-control layout and flat screens, but the rear view mirrors were small – a compromise between good vision and offering tree branches a small target.
‘The stubby gear lever had light, short action and the ratios were well chosen.
‘Town and country road handling was very good, albeit with some steering wander on the mud tyres.
‘A manoeuvering limit was the 12.8-metre kerb to kerb turning circle.
‘The OKA really hit its stars when the bitumen turned to dirt, where we found its gravel road handling was predictable, with straight and grab-free braking.
‘On a mine site the OKA’s supple, long-travel suspension worked quietly to cope with bumps and holes that stretched its oscillation to the maximum.
‘The gearing and low-speed torque combined to give it impressive climbing power with minimal need for gear-changing.
‘This truck has abilities beyond the experience of many who will drive it.’