I've been experiencing some vibration or roughness when driving at any speed. I've been unsuccessful in diagnosing the problem. The vibration hits a slight harmonic at about 60 MPH. It feels somewhat like an unbalanced tire or a like it feels when you drive across heavily grooved pavement on the highway.

Possibilities I considered:
-Wheels out of balance (tried rotating wheels, no change)
-Universal joint (jacked up rear of car, put in park, and tried rotating drive shaft by hand - does not seem to have any play across joint)
-Transmission problems as described in other postings (I hope not!)
-Engine mounts (all three look OK, best I can tell. Also put car in gear, held brake, and sped up motor in fwd and reverse, and saw some engine movement, but does not seem excessive)
-Ignition system (no fault codes received, pulled, inspected plugs, coils, wires, all look OK)

Based on other posts, I tried manually changing gears while at highway speeds. The vibration seems to change with the engine speed, not the wheel speed, so I think the problem is not with the wheels, drive shaft, or transmission. I also think I can hear some of the roughness if I rev the engine while in Park.

Whatever it is, it does not set off the check engine codes.

Any suggestions on what I should check?

I had the same problem a few years back with another car I had. It turned out to be the front tires. Only did it at 60 plus mph.

how many miles on car? and are you using original shocks?

Car has 110,000 miles on it. As far as I know, the shocks are original. I've had it since 60,000 miles. I suspected the tires, but that does not explain why the vibration changes with motor speed. Did you have similar experience?

I suspect that it's related to the tires.
How old are the tires?
When was the last time you had them balanced?

Tires are Michelin Energy MXV4 Plus

Two installed 11/04 at 81,000
Two installed 5/05 at 86,000

Now at 105,000, so 19,000 miles on two and 24,000 miles on two.

A tire problem would not explain why I can hear the roughness while racing the engine in park.

Inspect your crankshaft pulley vibration damper for cracks - it's the large pulley down low in front that the accessory belt mounts around.

Also check your shock and spring mounting perch for anu corrosion or cracks.

Spark plugs get changed - hard to inspect, and wires get resistance checked.

If it is electrical do you notice any abnormalities with the tach needle when at the rpm you get the vibration?

In my personal experience, on my c-class worn shocks seemed to exaggerate engine movement at idle - but things like that are hard to be absolutely certain about.

Are you sure it isn't the front flex disc? Tyre problems can normally be driven through. If you can feel the vibration through the seat of your pants and not the steering wheel then I would say flex disc. There is not always play in the propshaft. Look at it carefully with a torch, any cracks it's gone. Your mileage is about right for this too....

You know there are several things that rotate on the front of your engine.
Air Pump, Alternator, Power Steering , A/C Compressor, belt tension pulley, idler pulley. Any of these can go bad.

Racing the engine in Park is probably not a great idea. If you can hear the roughness from inside the car, then you probably can really hear it and probably locate the source by looking and listening in the engine compartment while somebody else revs the engine.

Steve

Check the motor mounts. They are fluid filled and can leak. Then they allow severe vibrations to be felt.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Wow! Thanks for all the suggestions. I'll check them out this weekend. Will post results.

During the last several months, I tried several things without any success. Last weekend, I looked at the mounts again with a mirror and flashlight. They all looked OK. I noticed that the transmission mount was relatively easy to pull, so I removed it. It looked OK except for a crack in the rubber on one side that may or may not have gone through. I figured it was a long shot, but I replaced it anyway, and all the vibration went away!

I would like to replace the flex discs in my 1997 E300 mercedes. When I look online I can only seem to find a replacement disc for the rear. Are the front and rear flex discs identical on the 1997 E320 (W210) ? If not, could someone please pass along the part numbers for both?

Thanks in advance!

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1987 560SL - 95K
1996 E300D - 183K
1997 E300D - 162K
1982 240D - 160K