JD440 high lift loaders model 831 vs 91; Which is best?

[Gil]

I have a couple of JD440 crawlers. One has a 831 Loader, one has a 91 Loader. Does anyone have experience knowing the strengths and weaknesses between these two loaders. I only want to restore one for use. My typical application is to skim off the top foot of topsoil and load it in a dump truck.

[Lavoy]

831 has more lift capacity, more breakout, bigger bucket, and in general is a heavier duty loader. Also more likely to be on a later model 440, but not necessarily so.
Lavoy

[Gil]

The problem I seem to have with the Model 831 loader is that once you lower the bucket to bite in and then start pushing, the bucket continues to dig down and it's liable to go to China. It seems to just flop over. If you try to gently feather it back up, it rises all the way to the surface.

If you continue the process you end up with a washboard digging pattern. I have resorted to pushing out the ground first with my bulldozer and then only using the loader to pick it up. Any suggestions on what I am doing wrong? I am usually only trying to dig out a half foot or so of topsoil.