Vibration in driveline

[timdsellers]

I have a slight vibration in my 01 gt when hitting 65 or above mph. Its not in the front end for sure. You can feel it on the gear shift knob and through the seat of your pants. My car is kinda a hybrid. Started out as a v6 but now has a new 5.4 2v and mach 1 tranny and rear end. I got it this way. Any ideas where to start? Thanks!

[06V6Andrew]

check the balance of the driveshaft. Happened to a Monte Carlo i had made it such a pain to drive

[bobtsgt]

Driveshaft or tire balance since its more MPH specific

[2Fast4You]

Agreed with the balance on the wheels or drive shaft.

[timdsellers]

Thanks guys. Im hoping its just the tires. They suck anyway and will be replacing them soon.