Bear with me, but in my mind I'm thinking that since the rear wheels aren't moving but you are giving it the gas, is the tractor actually "riding around it's own axle," so to speak? Is that why it happens so fast?
Thats correct, however it doesnt just happen like that: The friction of the rear wheels to the ground alone, arent enough to create enough moment to flip the tractor: You first must get all the tractors weight on the rear axle (front wheels off the ground) to get the grip you need to flip it, or the tires will just spin out.
This needs another factor: weight transfer. If you hook the chain above the centerline of the rear axle, you are creating leverage to pull the front axle up, which gives more grip, enough to backflip without spinning the tires.
In general, if you hook the chain at or below the centerline of the rear axle, backflip on flat ground is impossible.
If you hook it up just a little above the rear axle center line, you'll get some weight transfer, and the front end gets up a little, which in turn puts the drawbar down: So when the drawbar gets at the same height as the centerline of the rear axle, this effect is zero.
It gets dangerous when you hook up the drawbar so high, that the front end gets up way above the ground, shifting its own center of gravity closer to the rear axle.
My preferred method for heavy lugging is to use the 3pt bucket as ballast, and hook the chain to the top link A frame. It gives ballast for extra traction, and serves as a backflip limiter as well. I can control the amount of weight transfer by lowering or lifting the 3pt.
When not using the 3pt bucket, i pull from the lowest top link hole. mine has four holes, the lowest is about 6 inches above the rear axle centerline, which stops a backflip when the front wheels are less than 2 feet off the ground. this gives the most traction without getting unsafe.
