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  #1  
Old 02-07-2005, 07:56 PM
Veloce300DT's Avatar
TEAM MULHOLLAND
 
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Location: Sacramento-Bay Area Corridor
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What, if any, rear suspension components can cause vibration when worn?

Car-1984 300DT.
Ive been having a vibration that makes an appearance when I am accelerating full throttle, from either a stop, or when speeding up, and once I am at highway speeds above 75-80MPH, it becomes a constant vibratiion, that will only reduce to barely noticable levels if I fall back down to under 75MPH or so....

In preparation to determine the cause, I had all 4 wheels balanced, and aligned. Vibration is still present. The front end is new and no components show wear that might encourage a vibration. The rear suspension only has new shocks, the rest of it is original with 184K miles of wear and tear....

I have suspected that the vibration is either the result of worn drivetrain components, or worn rear suspension components. However, an examination of the drive shaft shows that all things are in proper condition..

So my question is what do I need to look for within the rear suspension to determine if anything there may be causing the vibration? What rear susp. components will cause vibration if worn?

Any advice highly appreciated.

Happy Motoring!

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Nate

1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


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  #2  
Old 02-07-2005, 08:07 PM
dieseldiehard's Avatar
Dieseldiehard
 
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If your wheels are not true this can result in vibration that rises as speed increases. the driveshaft might be out of balance.
In cases like this, find a shop that balances the wheels on the car, and they inspect the wheels using a strobe light to spot problem areas.
Last thing I would suspect is an axle, but don't rule that out
Did this start suddenly? Or was it always there?
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  #3  
Old 02-07-2005, 08:17 PM
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I will make a guess here and state that the problem is not in the rear suspension. Nothing in that system can cause a vibration unless the bushings in the system are completely trashed. Even in that scenario, it's difficult for the rear suspension to get "excited" enough for you to feel it.

Now for the tires. They are the most likely culprit. Now, I know that you had them balanced. But, the quality of the balance at most shops is not adequate for running the vehicle at 80 mph without feeling some vibration. The equipment and the operator must be at the higher end of the scale for you to come away with what you need.

The other situation with tires is the question of how round they are. You can check this on the vehicle with a piece of chalk. You need to setup a suitable stand for the chalk so that you can slide it into the tire. Have a second person turn the tire (vehicle jacked up) and move the chalk slowly into the tire until it just barely contacts the tire (it will only touch down through a 90 degree arc or so). Now stop the rotation. Turn the tire opposite the chalk mark and look at the gap between the chalk and the tire.

If the gap is 1/16" or less, you have an excellent tire.

If the gap is 1/8", you have a tire that you might start to feel at highway speeds.

If the gap is more than 1/8", you have a typical POS that won't go 80 mph without vibration.

Now, if this all proves to be not related to the tires, then I would begin to look at the drive shaft more closely.

Can you describe the location of the vibration more carefully? Do you feel it in the wheel? Do you feel it in your seat? Do you hear it in the cabin? More details can assist here.
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  #4  
Old 02-07-2005, 08:51 PM
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Stella!
 
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You aren't telling us if it is a buzz or a wheel-speed vibration but I'd bet, given the miles on the CD, it's wear in the driveshaft universal joint possibly coupled with bad/torn rubber in the center bearing support. The vibration occuring under acceleration and diminishing when the driveline is unloaded is the giveaway.

Give that center support a closer look...poke on it with a screwdriver. I'll bank that there's a tear in it somewhere.
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  #5  
Old 02-07-2005, 08:56 PM
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Quote:
Originally Posted by R Leo
The vibration occuring under acceleration and diminishing when the driveline is unloaded is the giveaway.
Randy, I read it as speed related. If he falls back down below 75 mph, the vibration is reduced.

Nate, I think we need some more info here.

Is the vibration related to speed, or is it related to load on the driveline?
Please clarify this because it is very relevant as to whether tires or driveline is the culprit.
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  #6  
Old 02-07-2005, 10:18 PM
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Stella!
 
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Quote:
Originally Posted by Brian Carlton
Is the vibration related to speed, or is it related to load on the driveline?
Please clarify this because it is very relevant as to whether tires or driveline is the culprit.
Brian,
You're the vibration man!

R
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  #7  
Old 02-07-2005, 10:19 PM
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Let me start by thanking all of you guys for sharing such great information!
And secondly I hope I can describe what im experiencing without confusing anybody... i will try to word this as clearly as possible while not leaving out any details.

The vibration seems to be related more to the load on the drivetrain, it is prominent upon medium to heavy acceleration at ANY speed under 75MPH. Once I have stopped accelerating from a stoplight (or in any similar scenario) the vibration goes away... while cruising at a somewhat constant speed, or accelerating very lightly (within a 5-10mph difference of the speed im traveling with light throttle pressure) there is NO vibration. So basically the vibration im feeling is only showing itself when I am accelerating from a stop with the pedal to the metal, or when I am traveling on a highway and want to pass someone and floor it. NOW once im pushing 75MPH, the vibration becomes a constant regardless of how im driving, although it is stronger when I am applying pressure to the gas pedal... (needless to say making highway driving rather unpleasant!)

As for how the vibration feels & sounds-
I can feel the vibration in my seat, the floor, and very precisely in the gas pedal. The steering wheel not so much. I had a friend drive the car while I rode in it, and as a passenger the vibrations could be felt in the floor and seats, esp. when sitting in the back seat with my feet under the front seat.
When accelerating the vibration is very "stuttery" feeling, i guess you coould compare it to a drum machine... precisely spaced vibrations that are spaced very closely together, and increase in intensity with throttle pressure. Once the car is running at 75MPH and above, the vibrations is the same as described above when pressure is applied to the throttle (passing, speeding up etc.) and once I am traveling a constant speed it reduces in intensity, and comes spaced out in "throbs" .... and if I decelerate from any speed above 75MPH by letting off of the gas pedal, the vibration becomes a constant (similar to the vibrations when under heavy acceleration) although not as strong.

Now, to make this seem even more complex, I will also add that the vibrations are much more prominent after traveling extended distances. For ex:
I frequently drive from Davis to SF, and SF to Davis. its about 62 miles each way on I-80. If im leaving Davis for SF, the drive to SF will be much smoother- the vibrations are thhere, but not quite as strong. However, at the end of the day, the drive from SF to Davis is much more "vibrational"

Weird weird weird.....

Believe me, if that description was confusing, you can only begin to imagine as to whats running through my mind in regards to trying to figure out what the heck is causing this! LOL

Thanks again, I hope that helps, and I look forward to more info!
Feel free to ask if you need clearer descriptions of the vibration personality!

Happy Motoring!
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Nate

1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


"The details are not details. They make the product."
-Charles Eames

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Last edited by Veloce300DT; 02-07-2005 at 10:46 PM.
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  #8  
Old 02-07-2005, 10:31 PM
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TEAM MULHOLLAND
 
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someone also asked if this vibration has always been there, or if has just started. over the 35K miles ive driven in the past year, this has only begun to become noticable tot he point of annoyance within the past 5K miles... when I bought the car it didnt vibrate at all.

Some other facts that might be of value:
Tires are michelin X radials (wanted MXV4's, but I needed tires urgently and the only way to get the MXV4's was to order them and id have to wait) They were purchased around 151K miles. Religiously rotated & balanced every 5K miles. Car now has 184K miles. A little bit more than 1/4 of the tread remains except for the following:

Driver side Rear tire is relatively new, was replaced at 181K miles due to a irreparable puncture.

Transmission & Engine mounts new, engine shocks new, and steering shcok has about 20K miles on it (replaced with front end rebuild).

Cheers!
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Nate

1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


"The details are not details. They make the product."
-Charles Eames

www.cbs.nu
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  #9  
Old 02-07-2005, 10:58 PM
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Nate,

Since this is happening under load, I am suspecting the drive shaft. It's possible a balancing wieght has fallen off or there is a problem with the center support bearing. Also look at the universal joints.

TimK
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  #10  
Old 02-07-2005, 11:17 PM
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Well, since I'm the vibration man............

Check back up and follow Randy's ideas (and others) on this.

Forget about all my BS regarding the tires. It's not the tires.

Vibration under load is definitely a driveline issue. This is further confirmed by the feeling in the seat of your pants and not in the steering.

Check for movement in the center bearing support, and/or a bad support bearing first.
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  #11  
Old 02-07-2005, 11:24 PM
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Thanks for all the help guys, I'll report back with any findings ASAP!

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Nate

1995 E420
1992 BMW 525i
1984 300D Turbo sold
1993 Volvo 244 sold
1995 Volvo 944T R.I.P!


"The details are not details. They make the product."
-Charles Eames

www.cbs.nu
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