Damaged trans?

I have a 3500 stall but starts pushing me through the lights at about 1800-1900 rpm. When it snapped I hit the rev limiter at 6200 then immediately shut it down. Oh I just found my problem by the way. The yahoo who welded my perch plates on for my relocation didn't do a great job at all. My diff is spinning on the perch plates. I bet it twisted changing the pinion angle then boom. Well he's done doing my welding. I don't see any cracks in the tailshaft but im going to drop the cross member to make sure. These are times I wish I had a welder.