My car is 2013 GT 5.0L, 3.73 without any mod. Since around 10k milage, I realized it got issue only in the 5th gear. When the car is not fully warm up, I feel the gear seems not sync well and I feel the stick shaking with a loud and unpleasant noise coming out form the gear box. This only occurs in the first & second time after start up. I can shifted to 5th gear smoothing if the car does not move. Anyone know what is going on?