If you have pounded on that thing at all you may have bent that drive shaft. Trust me, I have found out the hard way. If anything I'd have the wheels checked to see if they are true and also have the balance of the shaft verified. In my old 408 Valiant I could get the stock d-shaft/u-joints to last one solid day on the street with VHT enabled 205/75/14's. Once the air temp cooled down and the DA went down I'd break a u-joint or bend the shaft on the 1-2 shift.

If you have compromised an axle the car should be out of service until you get it fixed. Don't get me started on the stock axle with a stroker motor topic.