MB-Dude

In my '05 S55, I have an unusual shuttering or vibration at ~2500 RPM, regardless of transmission gear / vehicle speed. Thus, the vibration is probably engine related. Check Engine Light stays normal/not illuminated; no codes appear to be generated. During cold engine operation, the vibration is very noticeable, smoothing out somewhat as the engine warms up. Hard acceleration causes the vibration to also be noticeable. Revving the engine in Park, one can feel the vibration but it is mild. Thus, it manifests itself more intensely 'under load'. This vibration is not just a hum or minor sensation, but a true shaking. (Arguably, this is subjective but the shaking is not trivial.)

Forward engine mounts have been replaced (the LH one was completely shot and needed to be replaced anyway). However, vibration remains. Removing the belt for the blower lessens the vibration slightly, though it is still there. (This test was only performed in Park.) As a sidebar, we did discover that the idler pulley bearing for the blower belt is very wobbly and needs replacement.

When my repair shop had another '05 S55 in for repairs at the same time, the exact same problem was on that car as well, although the car’s owner is not complaining about the vibration and has owned his car since new. Nevertheless, having another car with the exact same problem was a bit of a shocker.

Since I've had the car only about a month or so I’m not sure if this is the nature of the beast or something failing. I’ve owned an S-class (W140, non-AMG) model before and it was smooth as silk through the entire RPM range. Just wondering if anyone has experienced this problem before, or if this is normal (though I seriously doubt it). Any and all comments are welcome, and thanks in advance.

Cheers,
Jeff B.

MB-Dude

Replaced Transmission Mount (MB p/n: 212.240.04.18) and the vibration disappeared. Smooth as silk now through the RPM range. The old mount looks fine, though it feels as if the mount is 'bottomed out'. It's possible the mount collapsed and the internal metal ribbing was transmitting engine vibration to the housing, which is bolted to the cross-member. Doesn't matter; problem solved. Considering the part lists for $49.50, was in-stock, and takes less than 30 minutes to change, I kick myself for not replacing it when I did the front engine mounts. Lesson learned - Replace all 3 mounts at the same time!
Cheers,
Jeff

jcjmw

Did you do the work yourself or take to the dealer? If dealer, what was the amount the charged?

MB-Dude

jcjmw - The transmission mount is ridiculously simple to replace, but I took the car to a local indie shop. Charged me a grand total of $85 labor. I would have changed it myself, but really couldn't get the vehicle off the ground high enough for me to wrench the old mount out. Of perhaps more importance... we're in triple-digit temps here in Texas and the possibility of struggling with a potentially stuck bolt, on my back, under a car, in that heat just didn't excite me! BTW, the engine continues to run very smooth through the RPM range, so I'm convinced the transmission mount was the primary culprit. Now to get that idler pulley assembly rebuilt with new bearings - but that'll be another thread.
Cheers,
Jeff