Bump in the front end? Pushing it?

[thirdstreettito]

Well, we got 5-8" of snow here last night and today. First time I've had to put the burb into 4wd. I swapped in a 40K mile rebuilt 10 bolt back in February; according the the dealer that did it, it's a 3:73. The SPID on the burb says it came with a 3:73. The NP208 was resealed 2 years ago.

Well, dad locked the hubs and put it in neutral, then I locked it into 4HI. The county doesn't like to plow, so the roads had tire track rows from where multiple car had driven. The whole time dad was driving the truck was lunging left and right. Mind you we don't drive in the tracks, we drive in the bulk of the muck, as to help clear the road. After going about 5 miles under 30mph in slush, snow, ice, and asphalt it started to do some really weird things. It got down to the point it seemed like the truck was pushing the front end to make it turn. I told dad to drive to some asphalt and idle forward, he did and the truck stopped itself, if the hit the gas it would then feel like we went over a lump in the diff or something. I hopped out and looked at the pinion yoke as he pulled forward and back a few times, just a little bit of play in it, nothing big or obvious. So what do you guys think it could be? Thanks, Bradley