Last weekend I was setting 4x8 posts. I put 5 bags of 90lb concrete in the fel to go to a post.. my slope was MAYBE 8’ in 30’... the bucket was about 24” off the ground and the tractor took off totally un controllable.. breaks locked riding on 3 wheels. thought I was gonna die. The bags were evenly dispersed. Tractor was in 4wd high range. What did I do wrong??