I am having some trouble with my 88 gt. At about 100-120 km/h it starts to almost shake........ I pushed in the clutch while in gear and while out of gear and it still shakes. any ideas??
I would check the drive shaft (ujoints) for wear. If you're experiencing shake in the steering wheel, check the front end, ball joints, etc. I've seen in a lot of threads where people had a vibration with no wear on the u-joints, but changing over to an aluminum drive shaft cured the vibration problem. It could even be that a wheel is out of balance. It could be a damper pulley, or a slightly bent transmission pilot shaft. The possibilities with all that stuff rotating are mind boggling, just check everything for wear or damage.
Shaking in the steering wheel and front end is mainly caused by worn out ball joints, although I would inspect everything. Jack up the front of the car and grab a tire at the top and bottom and check for play. You'll know right away if you have too much, as there should be very little if any. And yes, it would cause the whole car to shake.
You might check the output shaft bushing on the back of the trans-- My car has the same thing-- vibrations thru the shifter, can feel it on the clutch pedal, could tell it was coming from the back of the car....I checked the slip joint (front u-joint slides into the tranny), and sure enough, LOTS of play...see if you can shift it side-to-side...I would be willing to bet that is the problem. Good luck!
I had same problem, u joints were shot. i ordered ford racing aluminum drive shaft, figure if the u joints were going bad the drive shaft might get out of balanced as well so i just ordered it, not bad only about 2bills, and easy to install.