I'm not sure about visually inspecting them...as you would probably have to have some significant movement to see anything on the mounts.

SlickGT1 mentioned a diagnosis procedure....something like loading the driveline (foot on brake, while giving throttle) with the hood, while a second person watched from the side for movement. ---I can't recall the exact procedure, but search through his posts and you'll come across it! (It was for a 4.8, so I'm not sure if it can be applied to an I6....I don't see why not though as the physics are the same)

I to have started to notice an increase in vibration at rest (in gear), along with a slight pounding when I cross a set of ruts (in an intersection) at speed. The fact that I've replaced every link, arm, ballpoint and bushing front to back (not related to this issue) leads me to the only ones that are still original. I had planned to do the motor, trans and diff mounts this spring anyway.

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