If the tires were out of balance you should still have vibration with the rear in the air because the tires are spinning in either circumstance.
Glad you have it resloved, what ever the problem was or still is? :?
PS. Also if the rear of your car squats under acceleration it could be forcing the yoke farther into the trans. Usually I like about 1/2 to 3/4 from bottoming against tail shaft when sitting on the ground.