Honda Repair: Vibration appears to come from transaxle, wheel bearing, wheel rotation

Question
I recently replaced the right-hand drive shaft on a 1991 Civic (5-speed manual transmission) because it was showing the typical noise/vibration that became much worse when the wheel was turned.  After the repair, the problem remained the same.

I was about to charge into the wheel bearing when I performed the following test.  With both wheels off the ground and the car running and in gear, I stopped the right-hand wheel rotation, so only the left wheel was turning.  Viewing the right-hand drive shaft, it was wobbling even though it was not rotating.  I then did the same thing on the other side of the car, with the same result (i.e., the left-hand drive shaft was not rotating, but was wobbling).  This leads me to conclude that something inside the transaxle is causing the problem.  But I haven't clue as to what.

Oddly, I also have a 1998 Accord (5-speed manual) that has a slight vibration, which has been impossible to diagnose.  It's not the wheel balance, brakes, or driveshafts.  I'm starting to wonder whether I am dealing the with same issue in both cars.  Both cars have about 150,000 miles, but well maintained.

Any thoughts?

Answer
Chuck,

What kind of vibration are you feeling and when are you feeling it? I am not sure I understand your problem.
Here are some pointers:
Axles ususally dont cause a vibration. They just make niose when you are turning the wheel and you are on the gas pedal. (under load) When you did your test by stopping one wheel and observing the axle, well that is normal for the axle to wobble. You see with the car raised, the axle is not on a level plane,and it will seem to "wobble", That is normal. A wheel bearing won't cause a wobble either. They get noisy also.
A wobble us usually caused by tires out of balance. Also even if you get the tires balanced, you can still have a wobble. You can have a out of round tire, even though it came "in balance". I would look further into the tires.
I highly doubt it is something in your transaxle. If that was the case, the only thing that could be is a bad diff. bearing. And in that case, the seal would be hogged out from the loose bearing, and you would be leaking trans fluid everywhere. Are you?
Again, recheck your tires. I really think that is where your problem is.
Good luck,
Thanks