Maybe you have a couple problems going on or just one...
I had a lunch box in my front D30/06 Unlimited. In 2wd no problems. but engaged on a snowy covered highway I would feel it pull to the right on acceleration and when I let off it would pull to the left.(had a full Detroit in the rear if your asking) I lived with it/just saying.
With yours pulling in 2wd are you sure its not your tires/out of wack? A tire with bad belts or uneven wear, checkering, might cause it to pull left. Swap the backs to the front, easy enough to do to see if theres a difference.