OK everyone this is going to be hard to describe. Before I continue I have brand new wheels and tires and balanced correctly as well as the issue happened with the old set too. I have a 93 gt with 3.73 in the rear. The car is a manual but converted at some point in its life from auto to manual prior to purchase. Now on to the issue..... When I'm driving anything over 60 on the speedometer it's sounds and feels very strange, to the point that if I go past 60 it will blow up. Now this doesn't happened when I'm ripping through the gears going over 80-90. Is this a rear issue possibly? I feel it and hear it at a steady 60 and over and I have to constantly let off gas like the rear or Trans is gonna go. Trans was full inspected and it's tip top shape complete rebuild. I don't think it's the Trans at all but Idk. Help please.