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  #1  
Old 01-26-2003, 11:03 PM
curtsmb
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Vibration during acceleration

I recently bought an 87 300E w/ 121k miles. I experience an oscilating vibration, felt in the 'seat of the pants' during highspeed acceleration and high speed climbs. Does anyone have a suggestion for the cause of this vibration? Torque converter? CV joints? Driveline? Engine mounts? Warped rotors?
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Old 01-26-2003, 11:06 PM
Jackd
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I would rule out wrapped rotors.
The flex discs are a very good possibility. I would check those first.
jackD
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  #3  
Old 01-27-2003, 12:33 AM
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Could be the driveline going out of alignment. This could happen if your engine/tranny mounts are going soft and give under torque, or if the center support is letting the shaft itself wobble.

-anthony
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  #4  
Old 01-27-2003, 12:01 PM
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Location: Vancouver BC Canada
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You should probably go after this through a process of elimination

If it only happens on accelleration ayou can eliminate the brakes.
Now your left with the drive train.
Start up the car, put it in gear and attempt to move ahead 'with your foot on the break' Apply lots of power and enough break power that your barely moving.
I'd also strongly suggest you dont try this in your driveway. (just in case)
If there is an engine problem (eg spark miss) it should start to do it now and you can probably fix things up with a tune up

If all is well here I'd suggest that you take the car to a shop where they can run it with all four weels off the ground and have a look under the car at the same time to check out things like the drive shaft, transmission and rear end (looking and listening for the viberation)

Hope this helps
Barrie.
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  #5  
Old 01-27-2003, 12:34 PM
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I would make sure its not the wheels or tires. Try rotating and see if it changes the problem. Or, visually check this is by running the car on a lift at the speeds you have the problem and see. (consider safety first!) I had a rear left tire hop all over the place while the right side appeared to stand still it was so smooth. In my case it was actually something in the wheel carrier itself (bearing or flange - I don't know, I replaced the entire assembly) but I think that's a rare case. When the car is going uphill weight transfer will make rear problems more noticable.
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  #6  
Old 01-27-2003, 08:52 PM
curtsmb
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Thanks for the tips.

I just returned from the local MBZ shop, where they test drove the car and then raised the it on a lift and inspected the drive train. The mechanic found the flex disks to be in replaced/good condition but the dif and rear suspension bushings very worn and in need of replacement. It was explained to me that the worn bushings allow the rear drive train to flex under torque, thereby throwing the drive train out of alignment ..... causing the 'seat of the pants' vibration. I hope this relatively simple repair is the solution to the vibration problem.

Any comments?
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  #7  
Old 01-28-2003, 12:05 AM
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Just a heads up, if your suspension is all factory original there is a LOT of rubber that will ultimately get replaced to return the ride to "new".

My impression after reading these forums and personal experience is that vibration is something rotating at speed that is not balanced & rear end steer is usually the result of worn suspension rubber. Does the vibration occur at wheel speeds or about 3x faster (driveline)?

The differential bushings (4 total) are probably shot if they've never been replaced. There are two in the rear where 12 mm hex head bolts hold the diff to the subframe. Torquing these bolts will cause the diff to rock back and forth if they are worn out. Two mounts at the front of the diff do wear out but don't have the same effect as the rears and some mechanics never change them.

The rest of the suspension bushings are the 10 links of the multilink suspension, 5 per side as follows - torque, thrust, camber, tie rod, and spring link (lower control arm). Of these, the torque is the first to wear out, followed by the thrust, camber, tie rod, and lower control arm. However, the usual symptom here is rear end steer, not vibration.

If the center support bearing or mount are worn out (these are located under the exhaust heat shield), that could cause vibration at about 3x wheel speed. The bearing is suspended in a study rubber mount. Sometimes the bearing gets real loose or the middle of the mount separates and it feels like a thumping from the rear of the vehicle as the driveshaft 'whips' around.

This work can cost about $1300+ parts/labor or more, depending in your indy. If the camber, tie rod, or lower control arm joints are touched an alignment is necessary.

I would still rotate the tires to see if that changes the vibration or run the car on the lift and see how smooth the tires run. Overall, I would be suspect of any mechanic that I go to the first time, epecially with a newly acquired car. Moreso when he tells you need your rear suspenion rebuilt to solve an osciallating vibraiton... maybe I'm paranoid.
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Last edited by md21722; 01-28-2003 at 01:22 AM.
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  #8  
Old 01-28-2003, 12:24 PM
curtsmb
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Thanks for the warning.

The vibration is distint in that it only occurs under torque. It does not occur while coasting downhill at high speeds, or at level cruise speeds, but is noticable at high speeds under torque .... such as when accelerating on level or climbing at high speed. Otherwise, there are no other 'sounds' such as clunks, when abruptly starting and stopping.
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  #9  
Old 01-28-2003, 01:40 PM
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It could also be a bad rear shock, ie axel hop. The miles are right for shock replacment.

Haasman
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Last edited by haasman; 01-28-2003 at 02:13 PM.
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  #10  
Old 01-28-2003, 03:02 PM
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If you got the $$ to replace all the bushings and controlarms, then go ahead. Your MB will feel like new.
But if you only want to get rid of the vibrations, check ALL other possible causes first.

I had every single piece of rubber replaced for $1500. Read the thread HERE
What is not mentioned in this thread is, that before the repair, i also had the same vibration under acceleration as you describe. -And i still do..!

Freestyler
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  #11  
Old 01-28-2003, 03:12 PM
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When it comes to vibrations think in terms of rotating parts. Nonroating cars may transmit vibrations, but they are not the cause. Rear end suspension problems are known to cause klunks, thumping, or rear end steer. If the vibration is much faster than the wheels, its likely the driveshaft. Then check flex discs (loose bolts are possibility), center support bearing & mount. Freestylers experience is similiar to mine. However, I did not rebuilt the suspension twice to solve vibrations, so I was not disappointed that it did not.
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