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Old 10-01-2009, 07:20 AM
nhdoc nhdoc is offline
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Join Date: Dec 2004
Location: Nashua, NH
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1999 C43 AMG (W202) Is Finally Vibration Free!

Well, my C43 is finally pretty much vibration free

Since I bought the car last August it had been plagued with an intermittent vibration at speeds over 45MPH. First thought was tires of course, so a new set was fitted but that didn't help too much, maybe a little better. I then had them rebalanced with the Hunter road force system - again, an incremental improvement but still shaking. Sometimes the vibration was barely noticeable, sometimes it would feel like it was shaking your teeth loose.

I figured I would have the dealer look it over at that point. Their findings were that 2 wheels were bent, they recommended new motor mounts and also lower control arm bushings - I was dubious of their diagnosis but went along - I told them they own the problem now. $1350 later to remedy that list and it was pretty much the same as before.

I had told them from the beginning I was suspicious of the drive shaft as being the source of the vibration because I had noticed that if the car was driven, then parked for a while, then driven again it would be perfect. When I looked underneath I saw the u-joint is right over the exhaust system and concluded that it was probably the problem.

I found a used driveshaft on ebay which I bought for $115 (a new one from M-B was around $900 net - $1100 MSRP). When it arrived I could see its u-joint was extremely stiff and "worn in" right in the middle of its travel, particularly bad in one axis, and clearly worn out. The seller told me the car he pulled it from had 100K miles, about the same as my C43. He also told me he didn't notice that the u-joint was bad so he refunded all my money and told me to keep the part

I found a shop to rebuild and rebalance it for $367 including ground shipping both ways and did it. I bought two new febi flex discs and my dealer agreed to install it all for free as part of "goodwill" since they failed to diagnose the vibration themselves. I'm pleased to report that now the car is finally vibration free (well, as free as it can be - this car has an extremely stiff suspension so it "feels" every ripple in the asphalt as you drive and also the low profile tires take about 5 miles of driving to "smooth out" but it is finally acceptable to me).

The reason I am saying all this is because when they pulled the old driveshaft its u-joint was also stiff, just like the one I had rebuilt. My theory is that these "wear" because they flex so little normally that the u-joint just develops a "sweet spot" and then eventually becomes just stiff enough to induce the shakes. It can be temperature dependent too because the warmer the u-joint gets the easier it is to flex. On the C43, which has an extremely tight and responsive suspension, this was amplified, but I can conclude that on every other model, which uses the same driveshaft design, the very same issue is probably the cause of some of the vibrations we have all experienced. Those which replacing the LCA bushings "cures". I have always said the LCA bushings can't cause vibrations, but bad ones can allow it to be more noticeable. I suspect when people complain of vibrations and get new LCA bushings they really need that u-joint replaced instead. The LCA bushings "mask" the problem, like taking aspirin for a headache does. If you have a brain tumor the aspirin isn't going to cure it but will make you feel better temporarily.

Anyway, these are the guys I used and was pleased with, if you ever decide to pull yours out and check them:

http://www.thrashdriveshaft.com/import2.htm#MERCEDES

In most cases they do a core return type exchange but in my case the C43 is a somewhat unique model so I had to send mine in and have them rebuild it. They replaced the u-joint, carrier bearing, carrier and end bushings and balanced it as well as repainted it all included in the cost. I felt they gave good value for money spent and am happy to be able to enjoy the C43 the way it was intended to feel on the road.

The u-joints in these Mercedes shafts are staked in and not serviceable nor easily replaced, so that's why I had to find a specialist or would have to replace the whole thing with a new one. Finding a shop to rebuild them is not too easy...there are only 2 in the USA which I could find who routinely replace those u-joints. Here's some interesting background discussion and explanation of this:

http://www.thrashdriveshaft.com/Staked.htm
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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Last edited by nhdoc; 10-01-2009 at 07:44 AM.
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