I am working on a 2003 s500 with 99000 miles on it. I don't know the history of the car as it came from auction. the vehicle idles smooth and accels smoothly up to 3,000 rpm. either in park/neutral or on the road. but, at approx 3200 rpm there is a shudder type vibration felt throughout the car. it seems harmonic in nature and can come and go. Again, it is there both in park/neutral and on the road. When in park, and held at 3200 rpm, the vibration can be changed, almost eliminated for a few seconds by pressing the c/s switch on the console. Motor mounts, drive shaft joints, etc all look ok. No obvious signs of recent repairs performed

My 500E has a similar problem and it has me and my mechanic stumped. He thinks the drive shaft is out of balance. I suspect a tire problem. I'll post if we figure it out. (Since our cars are so far apart in years though my answer may not be much help.)

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Ben
Cincinnati, Ohio
1993 500E - Smoke Silver

the vibration feels like an out of balance issue like a harmonic balancer. The baffler is that it actually changes feel while in neutral and the c/s switch is hit, which controls trans shift points, etc. Feels like someone is shorting out cylinders to do a cylinder balance.

Try a new transmission mount. I've seen similar things like this before. Not a real risky proposition since the trans mount isn't too pricey.

have your mechanic look at drive shaft alignment//he may need to pull the driveshaft to chk u joints//there wont be slack in u joint but something that feels like stiffness in one spot of u joint..if thats the case then make sure
drive shaft is realigned befire installing new drive shaft...good luck

I appreciate the input on the driveshaft alignment, but I ruled that out because te vib can be felt in prk/neutral and can change with activation of c/s switch. I am guessing that it is caused inside transmission, however it drives and shifts fine except for the vib.