Originally Posted by YamahaR1
check the rubber mounts on your exhaust. unlike other cars, our exhaust doesnt "hang" it rest on cross members, when the rubber mounts go bad, you can feel a vibration on the shifter and under the seats. Unfortunately thats not the vibration we are talking about. we are refering to the vibrations from the engine at low rpms. the way i tested mine was by placing a jack under the exhaust to lift if off the cross members.
I think my vibrations also originate from the engine, but are magnified by the exhaust. Obviously I'm not 100% certain whether we're talking about the same vibrations, but my guess is we are. The exhaust rattling I was referring to was a completely different problem, just mentioned that because it proves that there definitely was/is some structural problem with my exhaust mounts.
I think with my car these issues are so tiny that the guys at the dealership don't even consider them problems. I've had various mounts checked a number of times and they haven't found anything. It seems like the car has to be very clearly broken for them to really find something, simply worn bits don't really register. As a result, I've kind of learned to live with these things since it seems I can't get them fixed anyway.
Just so that we're clear, the vibrations I'm referring to can be found in a couple of narrow "zones" between 1k and 3.5k rpm, and can mainly be heard/felt when the car is stationary in neutral gear.
For those of you who can hear or feel vibrations, could you try to estimate the frequency of the vibrations? This could help us determine the cause. Maybe someone with better understanding of engines and drivetrains in general and the S62 in particular could assist in troubleshooting?
For example, it seems to me that a broken flywheel would probably cause vibrations at the same frequency as the crank speed. The same would go for bad rod bearings. At least for me the vibrations I'm having seem to be half the crank speed (it's easiest for me to count the vibrations around 1200rpm). I don't know whether this could indicate issues with one of the camshafts?
One comment regarding the video that koolmofo posted: for that one the frequency of the drone correlates fairly well with the rotational frequency of the tires, and fairly poorly with anything else. One possibility could be that what you hear there is a tire imbalance inducing a drone in the exhaust note. Here are the maths:
At approx. 2200rpm he's doing an indicated 23mph, say 21mph actual speed; this corresponds to ~9.4m/s. With the circumference of a 275/35/18 tire being ~2.04m, this will give you a rotational frequency of 4,6Hz which is pretty close to what you're hearing in that video. For this to be related to the engine, even a fourth of crank speed would still be ~9Hz (2200/60/4) which is definitely higher than the drone you're hearing in the video.