I have a 4100 with 410 FEL.
The manual lists what the filled weight is, ands I don't have it in front of me, but I seem to remember it only being a few hundred pounds, total with the turfs.
I have 250 lbs of wheel weights that always stay on the tractor and another 850-900 lb concrete 3-pt ballast block that I put on when getting serious with the FEL.
If I am only toting around some brush or something bulky but light on the forks, I sometimes get lazy and leave the ballast block off. About 25% of the time I do this, I end up getting light in the rear end because the stuff I am moving is heaveier or more of it than I thought.
A heaping full bucket of dirt will easily pull the rear end up even with ballasted tires, I suspect. If you ad a tooth bar and start doing some real digging or root-pulling, you can get off balance even easier.
- Rick