Driveline Shudder/skip

[bogg]

We are on a 7000 mile road trip pulling our 30' 5th wheel, gross around 20k. I have noticed a few odd happenings and wonder if anyone has a clue what I might be looking at:

Around day 2 (now at day 15) pulling mountains in top gear doing 65-70 mph the driveline seems to skip a beat. No loud noise, just a shudder or loss of momentum during climbing. At first I thought it was just a bump in the road, but now I found that I can duplicate it on near every mountain climb, and my wife can also feel it. I just back off the right foot a bit and it does fine. I have it in Tow/Haul 100% when towing., but it will also do it if I turn the T/H off. Maybe the limited slip?

I am not sure if this means anything, but while watching close that day #2, I noticed a puff of black smoke out of the drive side pipe while starting out from a stop, and all that day everytime I went to start the truck (warm) the glow plugs stayed on like it was a cold start(10 times, then normal since). I also washed the truck for the first time today since then and I had a buildup of black soot on the body around the pipes and covering the white letters of the outside drive tires.

We have 65000 miles on her now and these events are not a normal experience for us. I think all my stats are in my sig below. 60,000 mile service done on day #1 and 65,000 mile service set for tomorrow morning at a dealer here in FL.

I might be noticing a bit of a rough idle this morning, but when you look too close those things are a little hard to pinpoint as real or not...

Any thoughts on that would be appreciated, especially the driveline issue.

Thanks