The fact that the brakes did not help tells the story.. You slid down the hill. Pressing the brakes will not help at all. You were NOT in 4wd. The fact you had nothing on the 3pt just made it worse. If you had proper 3pt
ballast it would not have happened even in 2wd with nothing in the bucket. If you load the bucket with something heavy you reduce the weight on the rear wheels. If you go down a hill with a loaded bucket in 2WD, and you don't have a very heavy ballast on the back you will slide every time in 2wd on a slippery hill.
There is nothing wrong with your tractor. You have just learned a valuable lesson. 4wd no matter what going down steep slippery hills if you wish to retain control.. Once the slippage starts, you cannot regain traction, hitting the brakes is the absolute worse thing you could do. You can drop the bucket to the ground to increase drag and also if you have something on the 3pt (throw out the anchor!) you can lower it to the ground.
As long as you can keep the tractor going in a straight line and there is not a drop off at the end, you can just steer and ride it out like you did.
My very steep gravel covered driveway will cause a runaway every time even with a 750 lb ballast on the 3pt if I have a full load (about 1200 lbs) of gravel in the bucket if I am in 2wd. I MUST be in 4wd to safely go down this hill forwards. Of course If I went down backwards It would be OK in 2wd.
If you have a hill this steep, there is never a reason to not have a significant weight on your 3pt. If you want to repeat your experiment just put a little weight in the bucket, nothing on the 3pt stay in 2wd and go for a ride!
