The UMAX Ultimate RV Project

U M A X - ULTIMATE RV ATW Conversion Project
18+ months in the making. July 2016 to present. Page 1 of 3.

Electrical System | Fuel | Climate | Water & Bathroom |  Features | Parts List | Recovery | Entertainment |
Cooking | Storage | Sleeping | 4 X 4 Features | Preventative Maintenance | Parts List |

Having owned a non 4x4 RV did you envy people with a 4x4 that could go places you couldn't go? Some tow a small 4WD for this very reason, seems a bit of a waste. Often you'd see people take their cruiser onto the beach for a day then have to return to their van or 2WD motor-home. 

What if you could stay as long as you like in luxury..

Raymond Island
Raymond Island 17-2-18

Q. What is the cost of a good 4WD and off road caravan? Now add you all you see below. You simply won't find features like a separate 5KW alternator or toilet that stores away to double the room use.

A rare combination of Luxury & Serious 4x4 Capabilities.

This page is more like a blog so we remember all the work done & write a manual.´╗┐ 

UMAX Ultimate RV Project

Colour Coded Siding Protection

Cinema Mode dimmable lighting

Above - Lighting in Cinema Mode.

UMAX ultimate RV

Ignore signs like this!

Seep my ass

This is a private project by a company director and will be sold privately.

Electrical System | Fuel | Climate | Water & Bathroom |  Features | Parts List | Recovery | Entertainment |
Cooking | Storage | Sleeping | 4 X 4 Features | Preventative Maintenance | Parts List |


Electrical System

Has its own Page.



Centre is main inverter, you can see the 12V house battery (48V bank is to the left out of view).

Lighting Options

Lights up

Cinema Mode dimmable lighting

Dimmer can adjust Cinema lighting - 100% Shown below is around 20%


Water & Bathroom & Toilet

Two rooms in one

A full sized marine toilet slides completely out of the shower area, (Patent Pending) the toilet resides under the kitchen sink when not in use. This is why the storage area under the sink is a sealed compartment as per marine use. Toilet slides on a drop down plastic running plank, once stored (pushed back) and locked the toilet can't move from its storage area. Even after a shower the running board is dry and you can step directly onto it.

There is a concealed switch to turn on toilet pump that's accessible once the toilet as been engaged.

Sliding Toilet effectively doubles the bathroom space.

Shower & Toilet

Note slider retaining lock above toilet. The slider bed was custom made from very strong plastic (same as cutting boards use).

Fresh Water Tanks

There are two fresh water tanks, 100L & 65L, valve selectable (near pump) or choose both (main and reserve, both fill via single keyed inlet cap).

Tanks have a cross feed valve (underneath near rear tank) that can be turned off in the case of trying to extract the very last of the water or one tank has been damaged. 

3 tanks

Waste Water and Recycling

Two waste water tanks, 55L Grey plus 55L black water = 110L Total.

Gray water can be pumped to flush the black water tank (separate pump and filter). Gray water is also used to flush toilet, this means stored can be round 100L.

The AC can produce water (dehumidify mode is best) which may be handy if you're in the middle of nowhere running out of drinking water, assuming you filter it.

To access find the hose (green stripe) that's plugged and remove the plug, also do this in the case the system is holding too much water and shows that error.


Water temperature and black water level Shower cold water mixing (left) and Black water level..

By setting the storage HWS to the desired temperature you avoid needing to fiddle with this setting.

12 O'clock is full hot (no cold added) and 9 O'clock is maximum cold added (=warm shower).

For maximum shower time you'd adjust  the HWS to max temp then adjust the mixer above starting at 9 then turning right to increase temp.

It's fine to have a shower with the bathroom as you see it in the image below, however for the sake of 10 seconds work to hang a protective shower curtain (supplied) you save a lot of cleaning and the area always looks its best.

Shower HWS 



  • Waterproof toilet roll holder under sink.
  • Gray water used to flush Full Sized marine toilet.
  • Spare main water pump supplied (and hose etc.) as this is the most lightly component in the water supply system to fail.
  • Outside shower, just in case you want to wash off some sand etc.

    Outside Shower RV
    Outside Shower next to cabin door  Shower is near entry steps.


 89665_tmc_electric_luxury_marine_toilet_24v_open   Handy Hints on the use of Marine Toilet


Lay some paper down first this creates a seal and saves cleaning. Use fluh pump in say 10 sec bursts (with say 5 sec between). Having problems, (bowl => 1/2 full with water, you can turn water off via valve..) wait 2 min then try again, this removes air locks. 


-- You can turn off the water supply (tap in-line near bowl) if bowl is filling up too far.
Patience is key and understanding that suction needs a seal. 

Powerful Pump out System

´╗┐Black water (Toilet) tank emptied via electric pump. 

Just put the hose into the dump point and turn on pump switch while holding hose.
-- The whole tank can be emptied in about a minute. 
-- You can then pump some gray water into the tank and repeat to rinse if required. (Much slower pump).
Tip: If the port pump seems not be working, check that you have water in the gray tank and try flushing the toilet, they use the same filtered feed point and there may be an air lock.
There is a gray water filter in the upper left hand corner that could need cleaning too, especially if you emptied tea leaves down the sink.
Worth nothing that whatever you put down the sink is used to flush the toilet so keep it to dish washing (try cleaning off most of the muck with a paper towel, saves water too).

HWS and Black Water pump White tank is storage HWS. Black water pump is above to the left.

-- Suggest pump some Gray water into tank then empty that out to flush the black water tank.
    (There is a separate "port" switch and pump for this function)
-- Gray water can be part emptied emptied by porting to black water tank (as above), or high flow dump valve below main fuel tank.
-- Bulk drain tap for grey water is fitted in case you have more than you can use in the toilet.

Storage HWS (Shown in above image)

  • 10L Storage heater HWS (1KW) 240V or 12V @ 25A. This can run at max temp if using 240V we recommend setting temp to shower temp so no cold mixing is necessary.

You can also run the HWS in 12V mode (70 deg is the auto max) by turning on the 12V breaker located near the heater.
HWS uses say 1,000W for 10min of every hour to stay full hot. This adds up so it's better to turn on say 1HR before you need it, then off when done. Even off, some hot water will last for hours for dishes. Suggest on while driving so water is hot when you get there and overnight.

The batteries can heat up the storage HWS water next morning with or without the engine (thus 48V alternator) running, this will take around 1/2 hour so you can set a timer (provided) if want the water hot as soon as you wake up.

Tip: Always better for battery life to start the engine and run in idle up mode for a few min in the morning before/as you power heavy 240V loads.
-- Like the coffee maker or microwave.


Getting it just right.

An easy and economical way is to adjust the HWS temp to your acceptable shower temp then you don't have to adjust anything else.

For 240V operation, there is a switch behind the microwave so you don't need to go outside, you can put the timer on there also. 

Washing Machine

Washing Machine

Washing Machine resides beside the shower.
Tip: Run the normally wasted water while the shower hoses heat up into the washer.

Empty washing machine hose via shower drain, if this position is ideal for you then easily fit a drain direct into the Gray water tank. 

Electric Storage Hot Water

Cold Normal or Filtered Water via Switch

Pump switch

10L HWS - 240V or 12V Storage Heater

  • Normal or Filtered water via sink tap is (electric) switch selectable (no need for 2 taps)
    -- Red indicator to remind you that pump should be off while traveling in case a pipe or fitting fails.

    Sink area

  • Toilet slides into shower area when required.
  • 1.95m H x 800mm D x 900mm W (Aprox.)
  • Suction fitting tea towel holder can be moved as required.

See also Climate System for emergency water source. 



Climate System

The living area is cooled by a 21,000 BTU Air Conditioner (6.05KW) and adjustable cooling fan in front of rear window.
Pictures may show the "Bio" model this has been replaced (Jan 2018) with a similar model that's a better fit, up from 16,000 BTU to 21,000 the control panel is mounted on the front.

Air flows via the rear window (sliding with fly screen) to the roof vent and/or cabin door when open (fly-wire with magnetic close in place).

You can via a special installed hook also have the main cabin door held partly opened with a safety chain for security.

Tip: It's best to park with the rear (or front if fitting the shades) of the RV facing full sun.
(Side on if using Awning is OK too)
-- Less surface area that can heat up the cabin, side on to full sun (unless using Awning) is a big heating load to try and dissipate.
-- Leave AC on in fan mode while driving in very hot conditions.
-- If parking side on to sun deploy the awning and park that side into sun.
-- AC filters can be cleaned (in place or removed for washing) without removing unit.
-- AC uses the water it produces (you can add more in very hot conditions via hose in under sink storage unit, use funnel NOT direct pressure from tap) to cool the condenser coil for more cooling efficiency.  Adding water is not necessary for the AC to work but will tend to stop it overheating in very hot conditions, water vapor & heat is exhausted outside. 

The AC will stop if the water it collects is more than it can use in the above process, open the outside drain hose.

Rear view 4x4 RV Air flow via rear sliding window / fan / top vent and/or main door.

Heating is via the diesel heater, we tested reverse cycle AC but this is far easier on the batteries and generally a far better way to heat.

Diesel Heater

  • 4KW diesel heater with 7 day timer (not standard, extra), can be used as ventilation fan.
    (Down arrow all the way then press it again)
    -- This unit can also display diagnostic codes (Press Heat button while heat it on), Press < and > at same time to clear codes.
  • -- Using a fraction of L/HR very economical and extremely effective heating.
  • AC modified to provide emergency water supply via tap outlet above rear drivers side wheel. (up to 30L / Day using Dehumidifier mode).

Caframo Sirocco Fan, force air from rear window, fan has inbuilt timer also.

Fan forced

Electrical System | Fuel | Climate | Water & Bathroom |  Features | Parts List | Recovery | Entertainment |
Cooking | Storage | Sleeping | 4 X 4 Features | Preventative Maintenance | Parts List |



Recovery Systems

  • 1750 lb - 7938KG (24v) Winch rear mounted so you can back out of further trouble!

    Fitting Winch Fitting he new Winch with custom mounting cradle..

  • -- After use suggest allow some time for 48V system to automatically re-balance before charging at high currents.
  • -- Using some pulleys you could winch forwards too.
  • Permanently mounted 4 X Treads and shovel (the easy way to get out of sand).

    Treads We got bogged on purpose just to try them and they work a treat!

  • Front winch point.
  • 2 X Spare wheels.
  • Remote controlled Search Light.
  • Rotating Beacon.
  • 2 X Reversing Flood Lights, next to reversing lights (New Feb 2018).
    They only come on in reverse provided you've switched on the master (high power lights, also enables driving lights..) switch on dash.

    -- NOTE Wheels on the right have RIGHT hand threads, on the left have LEFT hand (loosen the opposite way to normal)

  • Portable 240V air compressor that can actually get to the pressure you need (say 70 PSI front 80 PSI rear on the road, 30 PSI sand)
  • Various ropes, pulleys, snatch strap etc.

Testing December 2017..

Winch out 2 test


Fuel System - Diesel

  • 220L total over 2 tanks

100L main tank is supplemented by a 120L** tank on the passenger side of vehicle = 220L Total. 

Range is approximately 1,200 - 1,500km depending on your rush (80km/h speed is much closer to 1,500km range from our testing).

Tip: Best speed for highway cruising is 80-90 KMH = 15-16L / 100 KM. 100-110 KMH is no problem, naturally uses more fuel (approx 17L/100KM).


  • The 100L (main) tank can be topped up on the fly from the reserve tank.

The electric pump will move about 100L in 15 min. The Aux pump has a key safety interlock so you can remove this key so nobody can cross pump fuel (say you have children staying).

It would be possible to overflow the main tank (just as you could at a petrol station) which is the reason it's key protected. Unless parked were you can re-check the gauge by turning off / on the ignition while fulling it's safer to fill 1/4 of a tank at a time allowing 4 min, this excludes the last 1/4 to full as the amount of fuel from the last marker to overflowing is only a few liters.

While the pump is operating there is a large RED light on the dashboard.

If using the petrol gauge to estimate how much fuel you've cross filled remember there is a lag (unless you turn ign off then on) so we suggest you don't fill to more than 3/4 without either turning ign off/on or allowing 10 min for the gauge to average its reading. The same switch that turns on the cross feed pump (BIG RED LIGHT ON DASH) also allows the main fuel gauge to read the reserve tank. 

If the switch is in the show tank 2 on gauge position a yellow indicator will be on to remind you that your not looking at the tank that's running the engine, thus if left in that position you could run out of fuel and stall the engine.

To completely re-fill the main tank from the one on the passenger side  takes around 15 min. The 2nd tank is 20L larger than the main tank so this way you know you'll always have at least 20L for emergency use. If you run the 2nd tank dry you'll need to re-prime the pump via (squeezing once or twice) the in-line hand primer located above the tank, while running the pump.

Note: There is a fuel cut off valve before the pump, it opens when the pump is on. This stops any possibility of fuel syphoning from tank 2 to 1. 

When the fuel gauge is reading the reserve tank it's 1/4 of a tank pessimistic so you have a fuel margin.

Note the 2nd tank supplies the diesel heater and this should be taken into account in your calculations.
** This tank was purchased used (in perfect condition) as that's the only way we could source one. 



Kitchen - Cooking

 smeg-30-litre-convection-microwave-oven  Engel_95L_Compressor_Refrigerator Dometic Sink

  • Smeg 30L Convection Microwave 
  • Engel 95L Compressor Refrigerator
  • Dometic Sink

      They work in very hot conditions unlike some others. (Aux thermo cooling fan fitted behind fridge area.)
    -- 240V or 12V operation. Force 12V by turning off mains, plug behind toilet storage area (so move toilet into operation position to get to it).
    You may choose to run on 12V to balance power use loads between the 12V and 240V systems, depending on your usage requirements.

  • Electric induction hotplates (removable) supplied.
  • Dometic Rangehood.  (Standard lamps replaced with LED).
    Dometic Rangehood RV
  • Kitchen drawers / Overhead Storage / Push to open draws and cupboards (excludes overhead they open upwards).
  • Soft close duel garbage containers (one or both can be used for storage).
  • Soft close Pan Rack.
  • Wine Glass Holders

 Slide out BBQ

External slide out BBQ

Slide out BBQ - Gas bottle (Spare supplied) can be stored and used from above the spare wheel.



Other Features - Electric Awning with inbuilt LED lights

  • Ranger Roof Hatch with LED lights & Switch so you can use just the Range Hood lights if you like.
  • 2 x Side skylights either side of Main Roof Hatch.
  • Full sized windows (4 x 800mm x 1.4m, Rear 600mm x 1.8m, Bathroom 700mm x 1.2m, Door 540mm x 750mm).

    Full Sized Windows

    Full Sized Windows

  • Rear Glass - Upgraded to incorporate a sliding window 1400 x 320mm.
    -- Lockable with fly screen for better ventilation flow through, can be fan forced.
  • Entry to Cab from Cabin (Great for starting engine, use in emergency to gain access).
  • Aluminium blinds.
  • LED lights to number plate.
  • Auto Electric Steps into RV.
  • CB Radio.
  • CD / MP3 player in cab.
  • GPS in cab in place of rear view mirror.
  • Registered to seat 5 (Currently only 3 seat belts installed in cab, would require installing 2 to rear seat inside RV).
  • TV antenna (high gain with adjustable amplifier next to TV).
  • Yamaha Soundbar (Top of range very good sound) - Review
    Drivers: 2 x 19mm dome tweeters, 2 x 55mm midrange, 2 x 75mm woofers Quoted soundbar power: 30W x 2, 60W Subwoofer: 200W (no specs) Inputs/outputs: 1 x optical digital, 1 x coaxial digital, 1 x analogue (RCA phono pair), Ethernet, USB (service only), Bluetooth, AirPlay, MusicCast MusicCast file type support: MP3, WMA, AAC, FLAC, WAV, ALAC, AIFF Streaming services: Spotify Connect, Pandora, internet radio, others via AirPlay/Bluetooth Dimensions (bench): 950mm x 72mm x 131mm Dimensions (wallmount): 950 x 131 x 80mm Weight : 4.9kg.

    Sound and Vision
  • Spotlight (Marine, remote controlled at front).

    Spotlight, Solar, TV, Vents

  • Emergency light (Yellow, flashing at rear of RV powered on with spotlight can be overridden to always off).
  • Driving lights (2 X high powered LED).
    NOTE: You need to switch on the master (high power) light switch (on dash in a group of 3 including camera/rotating beacon) if you want them on when you select normal high beam. 
  • Reversing flood lights 2 X (New Feb 2018) operate only in reverse and only if you turn on the master (high power) light switch as noted above.

    LED Driving lights

  • Laptop Table (removable, magnetic & latch secured).
  • Magnetic locks on cupboards & draws (all that would open can be magnetically locked by simply turning on running running lights or main lights (i.e. you are driving).
  • Colour coded aluminium side protection to match powder coated wheels.

    Colour Coded Siding Protection
    Colour Coded Powder Coated

    Tire Pressure Suggestions

    • Highway @ 6500 Kgs. Front 70-75 PSI / Rear – 75-80 PSI • Dirt Roads @ 6500 Kgs. Front 60-65 PSI / Rear – 65-70 PSI • Off Road / Mud @ 6500 Kgs. Front 55-60 PSI / Rear – 60-65 PSI • Beach Sand @ 6500 Kgs. Front 50-40 PSI / Rear – 55-45 PSI* * Lower pressures may be needed in very soft sand. 20-25 PSI but speed must be kept very low and tyres re-inflated when conditions clear. A 285/70R19.5

    Source / background on tire / wheels
    While we were at it we fitted..

  • High power USB charger (next to bed).
  • Reading light and all lights can be controlled from the bed.
  • Reupholster drivers and passenger seats (plus matching seat covers) same pattern as couch/bed.
  • Fit new carpet (Genuine, you would not believe the price..) in place of vinyl. Fit extra second layer of sound proofing underneath carpet.

    Storage / Work Areas

  • 4 Cupboards (Push to open, 2 x 400mm x 540mm x 680mm H, 1 x 400mm x 200mm x 680mm H, 1 x 540mm x 170mm x 680mm H).
  • 4 Draws (Push to open, 400mm x 500mm x 100mm D).
  • Removable (Magnetic) PC Shelf.

Naturally you use the couch as your work chair.

PC Table - Removable

Electrical System | Fuel | Climate | Water & Bathroom |  Features | Parts List | Recovery | Entertainment |
Cooking | Storage | Sleeping | 4 X 4 Features | Preventative Maintenance | Parts List |

Large Kitchen Bench


Protective covering still in place. USB Charger next to rope storage units.

  • 7 Overhead aircraft style storage lockers (150mm x 850mm x 300mm approx).
  • 1 Sealed "Coffee, Sugar" storage unit under sink (130mm x 270mm x 160mm).
  • 1 X Rear Shelf below rear window 2.2m x 160mm x 160mm (Can be subdivided).

    Rear Shelf and Armrests Shelf. Note: Armrests are custom cushions.

  • 1 X 3 Hook Coat Hanger (between cab and shower areaa).
  • Boot storage (850mm W x 350mm H x 1.5m W Approx. usable) The boot also contains the batteries etc.

    Kettle shown for scale.

  • Long item Storage Area 1.4m x 60mm x 350mm (Polls etc., Under main cupboards).


Beds / Living area

  • Full width couch turns into bed 1.1 W x 2.3m L.
  • Front seats can be used as bed via insert that fits between driver and passenger seats.
  • Headroom for 6' 2" (Approx 1.9m).
  • Full sized shower / Toilet (1.95m H x 800mm D x 900mm W).

    Shower and Toilet

  • Cabin internal area approx 18 m2 volume (4m L x 1.9m H x 2.4m W).

    Cabin area


Extra Service Items

  • Preventative Maintenance - Overhaul Gearbox Transfer Box, Replace clutch, Bushes, Shockers.
  • The gearbox was in good condition given the low KMs. However the synchros were starting to wear, there was one gear (reverse) with a mark on it (Replaced = $1500), a few bearings were not 100% so ALL were replaced for peace of mind. Total cost for overhaul was in the order of $16k. We'd already done the clutch. Complete details available.

Even though the Fuso only had around 47,000kms when we started the project we've seen to:
(While working on it may as well "do the lot")

  • New clutch.
  • Upgrade 4x4 mode switching (a known problem in this model) so that it engages within a few seconds and disengages instantly. 
    Included new pneumatic module, vacuum hoses changed to rubber, new solenoids.
  • Overhaul Gearbox and Transfer case.
  • New shockers all round.
  • Full safety check & service.
  • New windscreen (even though the old one passed the roadworthy).
  • Various other small mechanical items such as suspension bushes.


Upgrades by ATW


Super Single Wheels, Parabolic Suspension etc.

Super Single Wheel Conversion

As all wheels are the same having 2 spares makes this RV virtually unstoppable.




Bull Bar


This RV project is based on the 4000 series mining bus made by ATW


ATW – Manufacturer of 4x4 buses and other specialized 4x4 vehicles for Eco-Tourism operators; commercial drilling, mining and mineral exploration companies. Our 4x4 buses are renowned worldwide for their safe operation, sturdy and long lasting construction, operating in extreme terrains and highly corrosive environments. All vehicles are based on Japanese or European 4x4 truck chassis that are commonly available through existing dealer networks and incorporate specially developed passenger modules by ATW.

ATW INCLUSIONS: • Duragal Frame built to ADR 59 ROPS. • 19.5” super single wheel conversion. • OH&S compliant, IP66 automatic electric step. • Low maintenance, tough and corrosion proof inner/ outer fiberglass body shell. • Offload body mounting system. • Reverse beeper & rotating beacons roof-mounted front and rear of vehicle. • “White noise” cancelling squawker. • All appropriate mine safety signage and Class-1 reflective side tape. •All metal access / egress steps and handles. • Water proof interior. • Sealed rear boot with LED lighting and wheel changing tools securely mounted. • Rotating beacon rear with all ADR signal lighting molded into body. • Sock ring pass-through between cab and passenger module. • Driver and passenger SRS air bags in cab.

We are not associated with ATW.

PDF Brochure for information only. Several items are different from our project 4X4 RV.

  • We understand the price for a new 4000 series bus is around $260,000 AUD.

Basic Truck Specifications before any alterations by ATW (many vary) PDF


The only downside is you will become famous :) We guarantee that people will approach you in places from Bunnings to Petrol stations mostly with thoughts like the random post you see below. The poster did not know us but their friend (our mutual) did and passed it on to us!

Random Facebook post 

FOR PRIVATE SALE $239,000 ONO (VIC/AU) O4O7O64361 - No sales calls.

Electrical System | Fuel | Climate | Water & Bathroom |  Features | Parts List | Recovery | Entertainment |
Cooking | Storage | Sleeping | 4 X 4 Features | Preventative Maintenance | Parts List |