Vibration problem

I recently had my 340 Duster 4 sp tuned. The guy needed to put it on a dyno but said the rear yoke on an 8 3/4 diff needed to be changed because it was showing some some wear and it was unsafe to dyno it. I had it changed but now I have a vibration at about 60 mph. I checked the universal joints and they all seem ok. The tail shaft on the trans does have some wear but I don't think it is overly lose, I have seen worse. Is it possible that when the yoke was changed it was put on to tight or too lose? I am not sure if it needs to be tightned to a specific torque. Hoping someone might have any suggestions.