Duallys are notoriously bad when it comes to traction in rain or snow. 400 lbs of sand bags over the rear axle will help. I think you have more of a traction problem than anything else. Back when I was a kid, I plowed snow for the town highway dept. We had a few Chevy dually C30 2wd mason dumps, 292 6cyl, 4sp trannys with 9ft Fisher plows on them. We would load them to the gunwales with 2-1/2 to 3yds of sand and salt and never got stuck. We would rarely have to put chains on them either. Im not saying you have to load your truck to that extreme, but some weight would help drasticly.
1986 M1031, Banks turbo,700R4,4.56 gears.