I have a strange problem with my 1993 300CE Cab w/91k miles.

The engine runs as sweet as can be,,, idles perfect, sounds great,,, never overheats,, doesn't burn a drop of oil. Engine harness has been replaced by PO and looks like new.

When I rev the engine in PARK or NEUTRAL (hot or cold, doesn't matter), there is a violent shudder from the engine at EXACTLY 4000rpms. The engine is shaking from side-to-side fairly violently.

The engine does not shake when the car is driving, even at high revs. I just took it out and drove the car to near redline in 1st, 2nd & 3rd gear,,,, it drives just fine. Suspension is fine,,, braking is fine.

Today may have been the first time I've ever revved it so high in Park,, so have no idea how long this issue has been present.

Any ideas?

Thanks in advance.