By David Wilson – First Published in Loaded 4X4 Magazine in 2019

Those folk in Western Australia have always been thinkers outside the box, a product of their distance from the east-coast centres of power and I reckon the product of a fair bit of “fuck-you”, since the State has been the engine room of the nation’s economy for decades. That same thinking has been the catalyst for the recent redistribution of GST revenues in this country, as it has always been a sore point that WA has been propping up other States who weren’t pulling their weight.

When iron ore mining was really starting to hit its straps in the early 80’s a consortium of miners got together to solve a problem that still exists today, the need for a vehicle with true 4WD capability and a three-tonne payload. We’ve all seen various adaptations of Toyota’s 70 series range evolve over the decades the vehicle has been in existence and it’s been used widely in mining in that time, but the payload is paltry, OK for the light jobs, not so hot for the intermediate.

So, in downtown Bibra Lake an industrial estate in Perth, the OKA Australia motor vehicle brand was created. That was in 1986 and a prototype was drawn up with plans to create a simple platform to build a range of different vehicle types, single cab utes, dual-cab utes, buses, trucks and any evolution of that your mind might think of. With a simple body/chassis bolt-together philosophy using big Allen bolts to change the configuration of the vehicle to any one of its variants, you could change the vehicle in an afternoon and still be legal, no need for an engineering assessment and a clumsy re-registration process as the job’s been done!

Clients were obviously going to come from mining, but OKA also held out great hopes for military sales and of course there would be a trickle of recreational users too, to supplement the necessary volumes needed for mass production.

I remember seeing for the first time the founding model, the XT, at an event held in Adelaide just after the dealer network was created and it was an impressive beast. I reckon that was around 1993. The local distributor was a company called Alltrac and the shindig attracted plenty of SA Government interest with the Minister of Mines attending to do the ribbon-cutting for the new dealership.

A few OKAs then found their way into Government agencies who used to do remote areas work across the State, based on the premise of having a robust platform with a decent payload. My clients working with the Environment Department liked the machine as it afforded them much more comfortable digs when they were doing their field surveys, but they were not without their problems.

OKA fanciers have a spin on the model nomenclature that came out with each new edition and it goes likes this; OKA XT = extra trouble, OKA LT = less trouble and the last model OKA NT = no trouble! Apparently, the worst offenders were the last ones, so steer clear of an NT if it’s offered to you!

OKA’s fortunes waxed and waned as the years slipped by with a licensing partnership with Hindustan Motors in India in 1997 having plenty of potential except for the execution being crude. In my research for this story I found a link to a Hindustan RTV ambulance (one of the myriad body styles this project spawned) with a bunch of pictures, one a safety message warning amongst other things of “Brakes are soft and sensitive, avoid pressing brake pedal too hard.” Something got lost in translation there, but the RTV project ran aground in 2008 as the buses built on the OKA platform were supposedly prone to rollover. The nail in the coffin for that project came thanks to an Indian Department of Transport scientific paper commissioned after plenty of RTVs turned-turtle, killing and injuring passengers. The report was pretty damning with its findings. I wonder though how much thought went into investigating the skills and licensing requirements of the drivers involved? As they say, there are always two sides to every story.

There were sales in New Guinea and an agency in Africa created, locations you’d think would be ideal for buyers of these robust-looking vehicles, but it was always struggle-street with only 500 vehicles built in its life and its reputation further challenged by an international scandal that involved a Malaysian partnership that turned sour. The scant reports I’ve read suggest a substantial misappropriation of funds, the disappearance of IP and production manuals and involvement of Malaysian Government officials suggesting corruption at some level.

For OKA lovers there is some recent news that a Fifth Generation platform has now been created with modern running gear and appointments and continues the rich tradition of this amazing vehicle. It now has some serious motivation running either a Cummins 6.7L (350HP) or 4.5L (205HP) turbo-diesels offering a 1,000Nm or 850Nm outputs and with Allison 6-speed automatic transmissions. They don’t come much tougher than that.

While OKA’s early history reads a bit like the best international espionage thriller and despite all the roadblocks put in its way, it still is a vehicle with a lot of supporters, one of their greatest is Rick Whitworth who hails from Melbourne.

Rick and his wife Sue planned for their retirement experience to be an international one, one that many of us can only dream about, pack the vehicle on a boat and transport it somewhere exotic and overland it near and far, so the vehicle had to be robust and reliable and able to be fixed anywhere.

OKA pretty much fitted that bill so in 2008 the hunt began for a suitable candidate. They wanted a bus body based on advice given by a few folk and that would make a camper set-up easy work, but the OKA body is made of steel and is heavy. A single cab with a body made of lighter weight composite materials and aluminium probably would have been a better starting point in hindsight to get the payload down.

Two early candidates were discounted, one a bus with brilliant mechanicals but a body full of concern and a cab-chassis that had OK mechanicals and no body and both priced towards the upper end of a basic used OKA. You can expect similar machines to cost between $20-40K and kitted out campers stretch to $100K or more depending on features, mechanicals and condition.

Luckily for the Whitworths (or depending on how you look at it when you consider the work and money tipped into this) in 2009 they got wind of an ex-tour bus that had fallen on hard times and was lying dormant in the snowfields of the NSW Alps. Daughter Nicky was working at Charlotte’s Pass and discovered the bus had been banished by NSW Roads because it was a little smoky! Her boyfriend of the time (a diesel mechanic) was of the opinion that the owners wanted it gone and a low-ball offer might just work.

Turns out the vehicle in its original life was used by a tour operator in Exmouth in WA, did a ton of work there before being bought by the Charlotte’s Pass operation to ferry skiers up and down the hills. When the Whitworth’s saw it, it had 500K on the clock. After purchase and a bit of detective work done, it was revealed it was really 1.5M K on the clock!!!

All that toil had taken its toll on the mechanicals and everything was shot, the gearbox, transfer case, the diffs and the motor. Incredibly though it was still driveable and with a deal done at a cheeky $10K, the Whitworth’s chugged off to Melbourne from the Alps and it was easy to see their progress as a smog alert was issued along their route. They were pulled up twice on the way home for the gargantuan amount of smoke coming out the back of the OKA, by the sounds of it good enough to hide a battleship in the North Atlantic!

It’s a testament to the Perkins Phaser diesel engine that it made the trip home and no doubt more than a few of the previous hundreds of thousands of kilometres before it, without turning up its toes. When the strip-down started Rick was of the opinion now was the time to get a new Perkins, replacing this 110 (that’s horsepower) variant with the more powerful 135 version. Nup, wasn’t going to happen, because the Perkins design of using a wet-liner cylinder sleeve in a block that miraculously was still perfect, meant the original 110 was going to keep earning its keep.

The 110 motor earns its keep (in legendary style) around the world in all sorts of vehicles, it’s a tractor motor and likely suffers huge neglect in its service with less than perfect owners, so imagine what life with the Whitworths might be with Mr Fastidious Rick at the helm? Perhaps 5M K???

With the decision made to re-sleeve and start from scratch with all the peripherals new or refurbished it was time to look at coaxing some more horsepower and doing it reliably.

Slow and steady might suit ploughing fields but it makes driving a chore on the highway so air, fuelling, exhaust and tuning had to be considered to fix the horsepower deficit. Fleetguard supply Cummins componentry and a new airbox was picked from their catalogue, an Opti Air 100 that features a bigger airbox and cylindrical air filter assembly with fewer restrictions, helping the OKA breather more easily.

A mate of a mate who could see some potential in increasing the size and type of the turbocharger got a batch purpose-built in China to their specification, a Garrett with wastegate and coupled to a matched intercooler. The intercooler has its own fan too, to belt through more air when the ambient temperature isn’t doing the job. The new Garrett price was a fraction of that quoted for repair of the old unit (try $750 Vs $3K), and it also meant that others could tap into this resource when the time came for their own overhauls.

With the exhaust taken care of better fuel metering was next and a set of Bosch injectors were installed along with a new fuel pump. All that fuel getting tipped in at precisely the right moment, at a cooler temperature than before and then igniting with plenty of ferocity, coupled to the newly boosted flows, meant the 110 once tuned was good for double the grunt it had when new in 1994.

Keeping the whole thing cool was a priority too as the likely destinations Rick and Sue intended visiting were going to be toasty at times, so the stock radiator was chucked out and replaced with a 4-core version that’ll never get unsettled, even in 50C temperatures!

When you up the ante on the horsepower that usually will impact further down the line, so some strengthening changes were required. The gearbox was replaced with a new Dana unit (the replacement cost cheaper than a rebuild) and now shifts sweet as a nut compared to the spoon in a bowl of porridge gear selection before and helped in no small part by ditching the original ceramic clutch and replacing it with an organic version. The transfer case was the original and rebuilt, as the New Process 205 used in earlier OKAs was much better than the Rockwell used in the last of the production. The Rockwell’s apparently consume a lot of power and are noisy buggers. Definitely don’t need that! Whilst the NP205 case was open, a 27-spline input shaft was installed, ditching the original 23-spline type.

Rick had the good fortune of taking his differentials to a Melbourne specialist for the rebuild process and got invited to do some of the work under the watchful eye of a master craftsman. As Rick said to me in the interview, “I like to tinker and disassembly and reassembly is a skill easily acquired when you read any of the technical data pages on sites like Pirate 4X4. Got a Dana diff? There’ll be a tear-down story about them, the only issue when it comes to diffs is the accurate setting up and shimming and that is the job of a specialist who can do it with their eyes closed!” Some jobs were farmed out, whilst Rick did a lot of the less finicky work himself, which he found fascinating.

Both front and rear differentials are LSD types too and the axles needed beefing up too, now sporting 35 spline ends which are way more robust than the stock 32 spline versions. The front end also got heavier duty steering knuckles because the originals were a bit underdone.

The suspension has had its fair share of attention too and now works a treat. OKAs wore elliptical (leaf) spring sets front and rear and he’s added a heavier top spring for some extra carrying capacity and had them all reset. The problematic bushes in the eyes of the leaves were remanufactured from XT to NT specification, 16mm up to 20mm and now they’ll never break. Another upgrade was to mimic the NT’s twin shock arrangement and Rick fabricated new shock mounts to accept the set-up. Now the Whitworths have a suppler ride with much greater control and less roly-poly on the corners.

The brakes were all overhauled, new disc rotors front and rear, calipers rebuilt and the same attention to detail on the transmission handbrake. Now some of you are likely wondering what the hell that is? Back in the day when 4WDs had hair on their chests, a trans brake incorporated a drum brake assembly that would act on the rear propeller shaft and hold the vehicle steady. Being up high it avoids the usual perils of a drum brake mounted at wheel level and that’s infiltration of dirt into the linings and shoes worn to bare metal in the blink of an eye.

Under the truck are a total of 230 litres of fuel spread across two alloy tanks, giving the vehicle a range approaching 1,600kms if need be. Despite the dimensions, Rick says the vehicle is economical and sips rather than slurps and puts the economy down to the way the Phaser produces its power now, not having to struggle up inclines and more comfortable battling head winds or overtaking semis.

Everyone knows the benefits of letting air out of your tyres when straying from the bitumen and having the ability to pump them back up at day’s end. That task is looked after by an Endless Air compressor coupled up to a 25L air tank which in turn supplies air for other tasks like Rick’s air operated door step for passengers stepping up into the bus which is ingenious, or blowing dust out of an air filter.

That’s enough about the mechanicals, what about the appointments for travel I here you say?

Always thinking of redundancy, the water they carry is stored across two tanks, with a total capacity of 180L. The theory is one big tank will drop the lot if holed, better to keep some separate. They are plumbed into a 12V water pump and direct flows up to the sink in the kitchen and also an external outlet for washups outside.

There’s a shower inside too when overlanding away from the caravan parks and the shower rose is a mixer style that can be taken outside for washing the armpits in the au-natural, in the au-natural surroundings, if it takes your fancy.

Because the OKA has a hot water service that’s either gas or 240V operated, they’ve got their gas provision supplied by two 9kgs bottles that can be swapped out quickly. Talking of gas, it also feeds two cooking appliances, a Thetford 4-burner stove inside and a slide out 2-burner stove/BBQ outside. Feeding a hungry horde of campers is no stress in this truck. Supplies can be pulled from the giant confines of a Waeco 110L fridge freezer, keeping the beer and grub cold as required.

Powering all this stuff is almost like paying homage to building a modern energy-efficient house. With a total of 405W being supplied by three Kyocera solar panels on the roof and then fed into an MPPT solar controller plus a 260AH lithium battery for storage, it’s going to take a fair while to run the system dry especially since it can be topped up off the alternator too. Thinking of redundancy again, if the starting battery failed the lithium system can be called upon to get them going again. Hell, the 12V supply also powers the electronically controlled pop-up roof and the kick out panel for the bed!

Keeping up with the news is easy too with a 19” 12V Firetail HD LED TV set installed inside that can be pulled down for entertainment, the signal enhanced by a wind-up Winegard antenna. And on that same night you’re glued to the telly and the elements are raging outside and it’s freezing cold, you can rely on the Eberspacher diesel heater to keep the OKA toasty warm inside!

Rick and Sue left no stone unturned with this build and the set-up is now insured for $120K and it looks every bit of that. They’ve been lucky enough to see plenty of Australia together in it and allowed the build to evolve based on their travelling experiences and what worked and what was a dud.

In hindsight Rick commented on the build this way. “I mentioned to you on the phone that the steel bus body conversion was not the best method re weight and effort. To start from scratch with modern RV motorhome panels would be much faster and probably just as strong”.

“If I were to do it again, I would choose the latter, but that is not to say that I am unhappy with the way it is. The huge benefit of the bus is all the windows, albeit I cut some of them down. They make it very open, airy, easy to keep cool and give great views”.

“You can also cool it down quickly with the very efficient engine driven bus air conditioner. The bus is well insulated and the diesel heater is great in winter. With everything shut except the hatch it easily keeps the inside snug even when camped in the snow”.

“All makes for very comfy off-road travel”.

2019 Footnote: There’s a bittersweet ending to this story as Rick and Susan never got to internationally overland the OKA as Sue passed away in 2017, just eighteen months short of retirement and the kick off date for the Grand Tour. I’m sure all of the 4WD community would join me in expressing our best wishes to you Rick and thank you for sharing this marvellous vehicle with us. With a bit of planning I reckon you’ll get the kids excited enough to fire up the OKA and do a lap of Oz in the memory of Sue!

2026 Footnote: It is with much sadness that we learnt that Rick passed away on Friday 28th August 2026 after a sudden and short battle with cancer. Hope the two of you are now getting that international touring time under your belts. Condolences to the family.