Company I worked at back in the '80s had 2 Trojan loaders, I don't remember the model, but a tractor-trailer couldn't carry 2 full buckets of coal. They had little to no brakes, of course. We had to take one back to the power plant from the shop, about 7 miles. We put an R-model with a beat up steel dump trailer in the front, my brother in the loader, then me in the service truck bringing up the rear. The plan was to put the bucket against the dump trailer, and use the truck's brakes.
The route was flat except for a high 4-lane bridge. The plan was to put the bucket against the trailer at the top and let the truck keep it under control all the way down. As we got to the top, the driver looked in the mirror and saw that huge bucket, and panicked! He started stuffing gears coming down the bridge, and holding the air horn down! When we got to the bottom we were doing over 60 in a 35 mph zone, cars scattering!
When we got stopped a couple miles later, the driver opened the truck door and started babbling apologies. My brother didn't say a word, he jerked him out by the hair and knocked him out with one punch half-way to the ground.