Clutch or motor mounts?

[Zaurusman]

Starting around a week ago, I'd notice vibration and shaking from the front end when letting out the clutch in first. A few days ago, it started in 2nd sometimes as well. Now it does it in third when under load. But when I downshift to slow down, I never get the shudder, even when shifting down a few gears and really revving the engine to test it.

This sound like the clutch or the motor mounts? The dealer can't diagnose, much less reproduce anything, so I have to figure it out instead....

TIA