5th gear vibration issue

[mazspeed]

Ok, so I have been having this problem with the car, and I think Kevin at CAR figured out that where the car is in motion in 5th gear, it will vibrate at higher speeds. It will do it down low a bit, but it's more pronounced at 85mph and higher. The tranny came from Keisler, and they told Kevin it was out of warranty, but they didn't shut the idea of them fixing it either. Don't know about that yet. My question is, do they have to rebuild the tranny for this, and what could be causing the issue? It's a TKO-600 in case you anyone was wondering.