Your drive shaft isn't rated to go that bad, that's why it's vibrating. When my buddy got his truck tunned we were dong 110+ and it started vibrating really bad. The turner was a very good mechanic and told us that there only rated for like 100 thats why they have a speed limiter of 97.

 

Dnyotech built a badass aluminum shaft for the hoe and I have had well over 130 mph with no issues