a pulsating throbbing sensation...

For those of you who love playing the "name that noise game," here's a fun one. At 55mph +/- mine has a vibration. Its slight, nothing to get me too concerned, but noticable. It also pulsates. Say on a 2 second interval. the vibration seems to start at the front of the car, then progress toward the back, then start over again.
I must add, this is an incredibly dangerous situation. The gentle vibration and rythmic pulsation is very relaxing. Like having one of those massage seats in the car. Dangerous cause it'll probably lul me right to sleep one of these days!

(hey, can someone make a car crash emoticon?)

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Paul
2004 E500 4matic; 72,000mi

Whatever the trouble, the frequency of the vibration is reaching a point of harmonic oscillation at that speed, which is why it appears to be smoothly and repeatedly moving about the car. Sort of like when a turbine passes through the "critical" speed zone as it winds up to speed. It could be a number of things, but I would look at the driveline first, and rear end. Check center support & joints for wear, and rear pinion for lateral play. If not those then maybe wheel bearings, but usually you can hear those..

I just changed the center bearing and support. Is it possible that i put it in slightly "off"? and yes, "harmonic oscillation" is precisely the words I was looking for! Personally, I sort of like it.

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Paul
2004 E500 4matic; 72,000mi

Could be an out of balance wheel too. I've had that happen a couple of times. and the vibration comes and goes at the same road speed.

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1978 Ford F-150 351M
2002 Kia Spectra 1.8l 5-sp
1985 Volkswagen Scirocco 8V 1.8l 5sp
1985 MB 300D Turbo California

"Die Natur verabscheut Vakuum"

Ok, its apparently not speed specific, I must have only really noticed it at 55 when I wasn't distracted by all the other noises.
It is there are lower speeds, resonating at the same frequency. Its actually a bit "stronger" at lower speeds. Now I think it actually comes from the back, and my best guess would be out of balance wheel.
The other possiblity, is that its the engine mounts. I know they are gone; just havent gotten to them yet. Could this be doing it?

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Paul
2004 E500 4matic; 72,000mi

If all the above cures do fix the simtoms, take at least two NO-DOZE for every 300 miles traveled. Do not exceed 600 miles traveled without a restful night's sleep. Consult your Doctor if you have problems sleeping and discontuinue use of NO-DOZE.



Sounds like a drive shaft, axle or motor mount problem developing. Check motor and transmission mounts before spending big money on axle shafts.

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

If this problem only became noticable right after you changed the centre bearing I would almost have to think its something you did.But that is not certain. At a minumin I would recheck your marks on the two piece drive shaft to make sure you assembled it identically. If not and you express the possibility it might be so you may be out of fundemental balance on that shaft. Coincidence of course is another possibility or perhaps if you have done some other work on the car? The reason I feel this way is your description is really good but that particular complaint seems rare to me.In my again limited experience the resonance seems to fade out in the same area it originates in like a bad tire at a certain speed after you pass through the critical speed usually. You also seem to be describing a self dampening resonance as well to some extent. That is not quite so common in my limited experience. Perhaps someone else will clarify the issue better. As the resonance dampens it might seem to travel as well. Indeed it may be actually travelling. Also you might want to have a really close look at your rubber driveshaft flex disks. That centre universal was checked and found to be good when you had the driveshaft off? Still can be checked on the car if not.

Ok, the truth is, the car had been sitting for 3 years, and only after I got the bearing/support fixed have I really been able to get it up to speed. So it really could be anything.
I thought the flex discs were ok, but in doing the support, it became clear that I needed to look a bit closer...
I tried to get the splines back on right. used lots of paint, but I may be off a spline. Is there any way to check that?
the uni. seemed fine.

As for no-doze. I could pay for that with the revenues from renting the car out for massage therapy

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Paul
2004 E500 4matic; 72,000mi

Well your never really driving it before the repair does open up a few things. If you could talk to the last guy that drove the car it might help if he would tell you if it was there before or not. If your spare tire is good you might substitute one wheel a day for example if you feel it may be coming from a tire or bent rim. Or at least have the tires present balance checked out first to see if that eliminates it. But the sensation of the problem having a two second interval period between events at the same speed kind of gets me off of tires. I like starting at the cheap items. A real good front end check should be done with any new aquisition for starters. I have to wonder if a really bad shock combined with a tire slightly out of round might do this as well? Maybe you have already eliminated that kind of thing. Not to worry. Nothing that time and money cannot find and fix.

You mentioned motor mounts in an earlier post. Check them closely. they may have settled so much that the engine oil pan is almost resting on the front crossmember. There is a mount there too. I have seen oil pans crack from the motor mounts being soo bad. This can get very costly to seal up properly again.

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

Are you sure you don't actually have ones of those vibrating seat cushions?


buy yeah, it sounds like driveline noise...

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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FACEBOOK: PANZER450

Sure feels like vibrating seats.

Anyway, I found this in a post about violent shaking at high speeds. Concerning track/guide rod mounts: "Another common complaint due to this mount/ball joint is brake pulsations and/or shimmy at a resonant speed around 60 mph. "

I was searching for the answer to the "clunk" under my left foot on slow speed bumps. Might this be the problem??????????

Violent front end shaking/55+ MPH/'82 300SD

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Paul
2004 E500 4matic; 72,000mi

Ok, the clunking up front was the lose caliper that tried to kill me. Definately not the vibration.

I moved the rear tires to the front, and it definately made a difference. So, had the tires re-balanced. The pulsation is Less, but not completely gone.

If one of my tires was not only out of balance, but also slightly out of round, could this be a cause?

__________________
Paul
2004 E500 4matic; 72,000mi