2003 Ram 2500 4x4, Cummins

I replaced my passenger side front ball joints this morning. I used the instructions here:
http://www.4wheeloffroad.com/techart...ade/index.html

as a guide.

I removed the axle with the hub/bearing still attached.

When I was done and had everything back together, I had a problem on the test drive. in 2wd, everything seems fine. I can accelerate hard and make full lock turns in either direction. In 4wd (4-high) if I accelerate any more than just barely off idle, I get a loud clanging sound...reminds me of a bicycle chain slipping, but much bigger/louder. If I turn, I get that sound, even at idle.

My first thought was that somehow the axle splines were not properly seated in the diff. So I took it all back apart and put it back together. When I put it together, I was careful to rotate the axle. When everything was back together, I noticed that I could spin that wheel and the front driveshaft would turn. So...the splines are at least partially seated.

Another test drive yielded the same results.

The hub is fully seated against the knuckle and everything is torqued to spec. So I'm not sure how the splines could not be fully seated unless something has moved inside the diff.

Any ideas?

At this point I'm at a loss...what could be going on?