285 Maxidyne.

Mrs, you are right in saying that truck speed limits, especially in the Eastern states, were a lot lower, e.g 80kph during that period.
Problem was, running Syd-Adel express, you simply did not have the time to gin about, company would get you out at midnight, still expected in next afternoon!
Which of course threw any attempt of economy out the door!
Gearing at 100 kph, where you could get away with it, Maxidyne was right up on peak revs, which was not what the engine was designed for!
1200-1300 rpm prolly give you around the 80kph, ideal for engine, couldn't keep times up though.
I will agree that even the old 237 Maxidyne/5 speed did a mighty job, didnt like strong head or cross winds across the Hay Plains, though
Bloke I shared an F model with used to have a hardwood wedge he would wire to the accelerator and just rest his foot on said wedge.
Used to bop along the plains until the revs got too low so then have to downshift, take next 20km to get speed up again!
Reckon weights would have been pushed out to around the 38 tonne on a tri!
Recall doing the weekender out of Adel, one time, overweight so was instructed to come over the Mountains (Mt Vic) , earned my pay that trip!
Dave

Even the 320 struggles on the Hay plains with a high load, but once across it feels like a power house

I dunno if there's a certain way to cross the Hay plains that doesn't catch the wind
It is always a slow grind in my old bombs

To be fair, Australian trailers are pretty high and back when people tarped trailers still loads seemed higher again


Paul

Yeah!
Even the tri axle 'Jumbo Pans' made pretty hard work of it!
Seems time of year had a bit to do with it as well, Aug-Sept used to be bad for winds
Dave

The tip-turbine fan is the whole heart of the system to maintain the lower temperature in the intercooler and to work efficiently needs unrestricted clean air. Without the air cleaner, the dirt would build up in the intercooler and block up in no time and the bearings in the tip turbine might be affected also. The cartridge in the intercooler is not cheap if you damage it.