Vibration on acceleration

subaru
forester

#1

I am getting some major vibration when I accelerate. The level of vibration increases with the level of acceleration - in other words if I am trying to quickly get up to speed, it damn near shakes itself apart. I’ve just replaced the front tires, had all tires balanced, had the front end aligned and replaced the front struts. Both front axles were replaced 2 or 3 years ago. The steering knuckle on the driver’s side was replaced a couple months ago. My guess is that either the axles are again needing replacement, or the U joints/drive shaft is the problem. What should I be looking for when I get my fat greasy butt under there to look?