My uncle shouts: "Whoa!"
I jump off the seat and have to use my entire body weight to disengage the clutch.
"Go!" he yells. I climb back up to peer through the steering wheel.
My uncle is on the tray of the truck stacking the hay bales neatly beneath him. My dad is walking alongside rhythmically tossing the bales up to him as if they are cotton wool.
My job is to steer the truck down the rows of bales around the paddock. Dad has put the truck into first gear and pointed me in the right direction.
Up and up the hay is stacked. My uncle is wobbling precariously and Dad is now throwing the bales up to an Olympic height. I concentrate on the driving.
Later on, Dad gets a tip truck and out on the road I sit on his knee to steer the truck at speed.
When tired, I climb up on to a pile of old rags behind Dad's seat for my afternoon nap.
Once my legs grow long enough I drive all by myself with Dad in the passenger seat keeping a close eye on me.
My dad and I criss-cross North Canterbury, going from farms to towns, quarries to construction jobs, the port to factories, through river beds for shingle and high in the hills taking superphosphate to top-dressing planes.
It is wonderful. Far better than school. Plus, I learn more. I see how men work, and how a good day's work satisfies them. I get to know machinery and how a big job is steadily chipped away until it is all done.
I learn that there are no boring or useless jobs, that the bigger the challenge, the greater the satisfaction when it is all done.
I learn what it is to do a day's work and to drink a cold beer with men after a hot and dusty day. And I learn economics.
The farmers grow the wheat, the flour mills make the flour, and the baker makes the bread. I see the entire production chain in a truck with my dad.
Our job is to get phosphate to the fertiliser works, the super to the planes, the wheat to the mill, and the barley to the brewery.
No one organises it. But the entire production chain is tightly synchronised by prices. I see the farmers figuring out what to grow based on expected prices and the cost of things. I see the trucking firms figuring out the best way to get the produce to market.
No one can sit back in Wellington and plan it all. They don't know what my father knows, which is the best way to town to beat the cops, the paddocks that get you bogged in winter, and how to get that old Briggs & Stratton motor on the auger kicked in the guts on a cold morning.
The price system enables each of us to use our best abilities to do our job while invisibly co-ordinating our actions to ensure they mesh to produce to best effect what people want.
Years later, I sat at the feet of Nobel Prize winners being taught economics. It wasn't a dry and crusty subject to me. It was a living, breathing subject that I had learned criss-crossing North Canterbury in a Bedford truck.
I got to see first-hand the total failure of centrally planned economies. They fail because they never allow the likes of my father to get the job done. Prices are set by central committee, not the interaction of free people pursuing their own happiness. The prices are wrong and, as a result, their economies planned chaos.
My dad died last week. Towards the end, I asked him if he wanted anything.
He said he just wanted to be back driving his truck. It made me cry. I felt exactly the same.