Truck Identity?

[Ausmick]

My grandfather was in the RAAF during WW2. He was posted from his squadron in Townsville QLD to Darwin and his diary showed the trip. Townsville to Darwin today is 2500km on a sealed road and a 30 hour trip. Their trip was on the ‘road’ in the picture during the wet season taking 11 days. I added in brackets their daily km. Anyone sort of have a guess at what sort of truck it was?

January 11 1942
Left Townsville 11AM lunch Reid River Tea Charters Towers. Have averaged 12 miles per hour. (138km)
January 12
Breakfast 4AM Hughenden Dinner 9.30 Richmond Tea 4PM Julia Creek. (516km)
January 13
Arrived Mt Isa, Frank and I to town. Landed a couple of beers. Town and country like Broken Hill. (258km)
January 14
Spine Bashed and played cards all day.
January 15
Left Mt Isa 12 noon arrived Camooweal 6PM. Looked the village over. Had sing song – no beer. (190km)
January 16
Crossed Qld NT boarder 530AM. Lunch at number 4 bore. Dinner and slept at 6A bore. (340km)
January 17
Lunch at Banka Banka. Plenty of Plain Turkys to eat. Slept at Elliott. (332km)
January 18
Lunch at A640 Bore slept at Larrimah. (238km)
January 19
Left Larrimah 2.20PM on sprit of protest. Tea at Mataranka, never dirtier. (75km)
January 20
Arrived Adelaide River to 2RPP. (309km)
January 21
Arrived Darwin. Went visiting saw lots of boys I knew. (114km)