Ru rammin 2?

I went to town last night on our poorly maintained snowy roads and shortly out of my drive way I noticed a grinding noise accompanied by a slight vibration. I rolled the window down and the noise was immediately amplified. I took the truck out of 4X4 and the noise went away. Then I put it back into 4X4 and was fine for a mile or so the the noise started again. The speeds I was going probabl never exceeded 35 mph and the noise would come and go at that speed until I headed home from town, then the noise got progressively worse and never quit again until taken out of 4X4. The t-case and front end have oil in them, the u-joints are all good, the brakes are good, the u-joints are greased regularly. I recently added all of the mods in mt sig and am still getting used to how the truck handles now. Did I just overwhelm my little aluminum t-case or is there a typical problem that does this? I have rebuilt a few of these t-cases and they are relatively simple, I will do the repairs myself but I want to know how to upgrade if I can. I have fourwheeled the truck some but nothing extreme. Everything too wild and I take the 79 ford. I do have 215k on the truck but that shouldn't wear out the t-case. They should last longer than that. I have changed the oil in the unit about once a year and used valvoline synthetic atf. Then to top the night off the truck picked up a death wobble on the way home, scaring my passenger nearly to death. He is a Dodge man from the word go and loves the 2nd gen 12 valves, has a 96 himself and is a mechanic and never saw the death wobble before. i said that that was just a dodge thing and mine always did it, along with about every other one I know of. He thought it was unsafe and needed fixed rightaway, I thought it was kind of funny.