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  #16  
Old 10-18-2002, 03:40 PM
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TANK,

I appreciate everyone's comments.

767Flyer and myself BOTH had incorrectly installed front lower control arm bushings. The bushings are part of our problem, but not the ultimate fix. Both of us are still working on it.

I have not tried the center hump test, I just put my hand on the side of the center console. I do get SOME vibration there, but its not bad compared to when I've got rear tires out of round... Do you feel ANY vibration there? I have the parts on my shelf, but have not yet installed them as I did not think driveshaft would cause steering wheel vibration....
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  #17  
Old 10-18-2002, 03:42 PM
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John,

Underneath the exhaust heat shield is the center support for the driveshaft. Its a rubber donut that bolts to the body. A bearing that is mounted to the driveshaft fits inside this donut. When its really bad, the donut has broken away from the mount or the bearing howls.
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  #18  
Old 10-18-2002, 03:48 PM
TANK
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Sure John, to the best of my recollection, the driveshaft, really 2 driveshafts joined - if you will, has something called a center support loop. Within this loop is a rubber "grommet" that holds a bearing by which the driveshaft turns. On my car, the rubber had a slight dip in it form age or sitting- I am not sure which. This defect gets worse with time exponentially and causes vibrations everywhere eventually. It's not difficult to put on, just time consuming because you have to remove stuff to get to it. I am also going from the experience of a 126. I have not owned another mb and assuming others are set up similarly if not the same. There may also be a pic of one on fastlane parts if you do a search..

md21722 - Yes, I did have vibration in my center console and pass seatback also.
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  #19  
Old 10-18-2002, 03:57 PM
John_Schwarz
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Thank you for the explanation. The car is going into the shop to track down a vibration when the car is put in drive/reverse. In that post, everybody is come back to the ignition as the problem. Overall, the ignition appears to be functioning well.

I'm leaning towards a more mechanical issue such as the exhuast system and transmission have some counter tension. The tranny was replaced about a year ago along with engine and transmission mounts. The tech is guessing that when the car was re-assembled, the transmission and exhaust were tightened with no stress on the chasis. So, when the car is on the road, new stresses, hence the vibration.

Anyway, we're going through all this on Monday, so I'll the center loop as something to check. A couple hours of the car in the air and a Tech at my disposal - priceless! Actually, I'm quite sure they will find a price!!! Thanks for the help.
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  #20  
Old 10-18-2002, 04:38 PM
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Location: Plano, TX
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I've had the steering vibration across two sets of tires, so it isn't that. It's also been consisent across front-to-rear tire rotation.

I've got new tierods and drag link, and just put a new steering shock on while I was under the car for the 120K service in August. (Man I hate changing the transmission fluid, has to be my least favorite task.)

I think what it boils down to is that everything rubber deteriorates on an older car. The only way to make it feel like new is to replace all the rubber. So subframe bushings, lower control arm bushings, the various links in the rear suspension, etc.

I know what you mean about newer cars feeling so much better. My other car is a '98 E-class, and it feels so much smoother & tighter than the 124. It's not so much that the 124 is bad, it's actually pretty reasonable, but the new car is just so superb. It's so smooth - I can't tell the difference between 50MPH & 100MPH, side winds don't phase it. I almost understand why people buy new cars...
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  #21  
Old 10-18-2002, 04:55 PM
John_Schwarz
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Hi jcyuhn-

Here I am fighting the new car bug and you say how much better your '98 feels!!!

I agree with you on the rubber parts. In another post I'm trying to get a vibration taken car of at idle in drive/reverse. If we can that taken care of, then I'll start in on the suspension (struts, shocks, bushings, etc.). If vibration at idle can not be located, then I'll start looking at new (or newer) cars.

Before buying the '95 E420, I test drove a '98 E430. That car seemed "shift happy" with the 5 speed transmission. In city traffic there were many 2-3 shifts. I opted for the '95 because the ratios were abit wider, less shifting and it seemed like a smoother ride.

Since you have both, how would you compare the daily operation of the two vehicles?
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  #22  
Old 10-19-2002, 05:02 AM
LarryBible
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md21722,

Since you have already had the wheels rebalanced at a different shop, it is time to find a 9700. I disagree about this being done ONLY by an MB dealer. There are plenty of 9700's around. To find one go to: GSP9700.com There is a locator on this site that will tell you where there is one in your area.

Remember, when you are replacing/repairing such things as suspension components and steering couplers, you are not going to the source of the vibration, you are only correcting things that are making the vibration slightly worse. Don't get me wrong, all these things should be in good shape. But, you could easily spend a fortune getting all these other things in perfect shape, but will still have a vibration if there is a source of vibration.

By far, the most common source of vibration is the wheels and tires.

You did not say what kind of tires you have.

Good luck,
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  #23  
Old 10-20-2002, 01:47 PM
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Thanks for everyone's comments.

The rims are new-style factory 124, with Michelin MXV4+ tires.

My mechanic was too busy to rotate or re-balance my tires. I re-checked the front end again and noticed loose wheel bearings. I tightened them, and there was a SMALL improvement.

More troubling, is I believe my transmission and/or driveshaft is a big part of the problem. The vibration becomes an issue after 60 MPH. Shifiting manually into 3rd gear makes a distinct improvement in the vibration - at 60-77 MPH. At 77 MPH, the car does feel a little wierd in third, but at 72, it's much more "solid" feeling. I think at 77, a resonance might occur from tranny to rest of car.

The tranny has known issues, including reproducable:

(1) rolls backward downhill on grade (easily)
(2) rotating driveshaft makes "klunk" noise. driveshaft havles themselves fit good - verified by my mechanic who "promises me" its the tranny

and intermittant occasional problem listed above, and a fast, harsh vibration (happened less than 5 times) when floorboarding car onto freewayat it reaches high RPM - makes me pull back off gas pedal - then goes away

I've replaced other suspension components in the past to cure various other problems including harsh intermitant vibration (front lower control arms), wind sensitivty/ride height (shocks, spring, subframe mounts), extra play in steering (worn components). Now its "tuned" into this. Most people don't seem to think driveline can cause steering wheel vibration, and I'm won't change the tranny specifically to reduce vibration (the vibration is annoying, but tolerable). I'm going to replace it because its starting to act up more frequently and I don't want to be stranded somewhere should it finally go, particularly with winter coming, and trips to family/friends for coming holidays.
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  #24  
Old 10-20-2002, 03:16 PM
TANK
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Quote:
with Michelin MXV4+ tires
Can't go wrong here! I still think it's a combo of your lower ctrl arm ball joints incorrectly installed and perhaps the ds loop and bearing and/or dive shaft is out of balance...
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  #25  
Old 10-20-2002, 06:00 PM
LarryBible
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I'll try one more time.

If it is not a part that rotates more than 360 degrees constantly as the car goes down the road, it CANNOT be a source of vibration. It CAN, however, be something that will allow the vibration to be more noticable.

The rotating parts to which I am referring would be tires, wheels, rotors, bearings, driveshaft and associated components, halfshafts, transmission rotating parts, engine rotating parts, rear axle rotating parts.

So you have two categories of parts, rotating and non rotating.

By far, the most likely vibration culprit is the wheel/tire combination, the second most likely is the driveshaft components.

The worst offender for non rotating parts are the motor mounts. Anything else in the suspension and steering system can aggravate mostly wheel imbalance.

Another thing you should pay attention to when analyzing a vibration is its speed. The driveshaft spins at an RPM about three times greater than the wheels. You should keep this in mind when trying to isolate the source.

Outside of bad motor mounts, you are chasing your tail replacing all sort of non rotating components in an effort to eliminate a vibration. Although these components should, of course, be in good condition, you cannot eliminate a vibration by replacing them. If you are on a campaign to replace every non rotating part that might be causing exagerated vibration, you are on an almost endless path until you correct the ROTATING SOURCE of the vibration.

Good luck,
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  #26  
Old 10-20-2002, 07:21 PM
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Larry,

I'm not sure why you have to "try one more time". I agree with you.

I did NOT change suspension parts to cure vibration. The ONLY exception was the front lower control arms, and that may not even be considered a vibration. It was a thumping/vibration that occurred at lower frequency than vehicle speed, and replacing those parts cured THAT problem, and I haven't experienced anything like it since.

Tranny behavior is getting worse and will be replaced. Whether or not it makes my vibration go away is secondary to having a solid, good working tranny.

One question Larry - can you say one way or another if tire balance can cause an intermittant vibration? (assuming wheel weights are NOT flying around on the rim). I've always believed tire balance is either good or bad, it ain't intermittant.

Thanks.
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  #27  
Old 10-20-2002, 07:23 PM
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TANK,

Why do you call the driveshaft support and support bearing a "ds loop". I've never that before.
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  #28  
Old 10-20-2002, 07:40 PM
John_Schwarz
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Hi Brian,

Wheel balance / vibration issues occur at different speeds and at different temperatures. As the tire heats or cools down, the PSI changes and this can influence the tire balance or make flat spots more noticeable.

If you replace transmission, have them replace transmission mount, flex-disc, center loop (where the two dive shafts are joined together) and differential mounts. Short of the axels, this take care of every rotating part past the engine. Except for the differential mounts, all of this stuff is coming off anyway, so replacing them doesn't add any labor cost, just parts.

Also, have a friend idle the car at the various RPMs where you know the vibration kicks in. While he/she is idling the car, put your hand(s) on the engine (like the plastic covers over air filters & wear gloves!) and see if you can feel a vibration with the same frequency/characteristics that you're feeling while driving. If you do, but you don't feel the vibration in the cabin or steering wheel, then know at least the motor mounts are doing their job. Likewise, it is something past the engine which is magnifying the vibration while you're driving.
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  #29  
Old 10-20-2002, 11:49 PM
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If both front tires have minor imbalance, it can cause a small intermittent vibration in the steering wheel. I've had this happen on one of my non-Mercedes cars. The relative position of the two front tires makes the vibration come and go. If one tire is "pushing" just as the other is "pulling" the two working together can generate enough force to be noticable in the steering wheel rim. Drive around a bend in the road and it disappears. The outside tire has travelled farther than the inside, and they are no longer aligned just so. My old Taurus SHO used to do this when both front tires were ~1 ounce or so off. Not enough for either tire to cause a bad vibration on its own, but enough for them to jiggle the steering wheel by working together.

- Jim
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  #30  
Old 10-21-2002, 01:54 AM
TANK
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Why do you call the driveshaft support and support bearing a "ds loop". I've never that before.

Sure md21722, it's actually a term from the far reaches of the "Tank" brain and NOT and industry wide term. I used to be in sales and now I am in computers. Since I've been in this industry Ifor a couple + years now, I have a tendancy to make acronyms out of everything.
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