My car vibrates hard at 55. I can feel it in the shifter and center console. Does this sound like a bad tranny mount or what could it be?

 

Probably not the trans mount. Mine was broken on an m6 and it drove fine. I would check the tie-rods. Jack up the front wheel and wiggle it left and right. If it will turn at all without the steering stuff moving, the tie-rod is shot which means it will be wiggling freely like that while you drive. The other possibilities are an alignment, a bulge in a tire, or an incorrectly balanced tire (one of the weights came off). I once had tired mounted on a corvette and the guy did a sorry job and the vibrations became noticeable at about 60.
If your vibration is specifically in the trans, I would suspect maybe a shot u-joint. The driveshafts are also balanced and whatever way they come off, they have to go on again, but I think the weight is welded on it.