Driveline vibration above 75mph.

[TheJDMan]

I have a drive line vibration that starts just above 75mph and just gets worse. I did not have this problem until I installed my T56. When I was running running my T10 the transmission was angled down 3deg and the rear end is angled up 3deg and I had no vibration. Now with the T56 the transmission is angled down 2.5deg and the rear has not changed. The driveshaft is new from Strange so I don't think it is the problem. I'm wondering if the longer transmission at 2.5 deg and the shorter driveshaft all combine to cause my vibration. Any advice would be appreciated,