PLEASE HELP 300 se vibrates starting at 25mph all the way up - PeachParts Mercedes-Benz Forum

boem · #1 08-22-2010, 01:50 PM

I have a 300 se, with 212k miles I owned this vehicle for the past 6 years.

The vehicle is well maintained and I enjoyed it much for the first 3 years.

In the past 3 years the car is seating in my garage because i don't have the heart to drive it and cause more damage.

The problem with this car is a vibration that starts at about 25-28 miles per hour, it is a severe vibration that you can feel in the driver seat it comes from the back of the car.

My old mechanic tried fixing it and I feel as if I was taken for a ride.

It all started after replacement of the flex disk. by same mechanic.

since then the drive shaft was replaced with a new one, the differential was replaced, transmission mount also replaced, one rear cv axle shaft assembly. The problem still there. I am desperate, I love this car and spent lots of money on it, I want to put it back on the road but the vibrations simply takes the car apart ( loosened up my dashboard)

Please, If anyone knows what can be the problem, Please help

PS- It is not wheel or tire problem, car shakes on the lift without wheels.

I suspect is is the drive shaft but i am not sure and don't have extra bucks to waste.

Thank you very much

I will post the solution once problem solved to help others.

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Stretch · #2 08-22-2010, 02:04 PM

Well if all the work that has been done has been done correctly I guess you need to start looking further forward. Gearbox mounts and engine mounts?

Does the engine dance about a bit when you rev it at a stand still?

boem · #3 08-22-2010, 02:15 PM

Thank you Army

I am not sure the work that was done was done right, same mechanic did a few mistakes that were easier to find.

S-Class Guru · #4 08-22-2010, 02:28 PM

Boem, if the problem did not exist until the new flex disc was installed, then that area is the best plasce to look for improper installation or bad parts.
A vibration starting at about 25 MPH sure sounds driveshaft-related.

First thing might be to check the bushing on the end of the driveshaft that aligns the shaft with the tranny output shaft. Could have been worn out or damaged when the new flex disc was installed.
Where did you get the new driveshaft? I understand they must really be rebuilt properly to avoid imbalance. The new shaft probably did not come with the new front/rear bushings I mentioned above.

The two halves of the driveshaft must be mated properly to each other to avoid imbalance. Is yours marked to identify which splines to align when joining the front/rear parts of the shaft?

But...... if the problem started just after a flex disc install, with the old driveshaft still in the car, then that driveshaft was probably not the problem.

DG

Stretch · #5 08-23-2010, 12:44 PM

Hi Boem,

I forgot to say - welcome to the forum - sorry!

If the problem is speed related - rather than engine rev related - or in which ever gear related (if you see what I mean) then my #1 suspect would be the propshaft.

If someone has taken the two halves apart without marking where the splines should match then you are in a bit of trouble. The same goes for if someone has removed one half of the propshaft and replaced it with another without balancing...

From my reading of the factory service manual (FSM) on the balancing of engine parts they only seem to prescribe static balancing - not dynamic balancing (like your tyres). This is quite straight forward if you can find a way of letting the propshaft rotate freely (so mounted on low resistance bearings or between lathe centres - long lathe!) and refitting the join in the propshaft so that the shaft will spin freely and not favour a particular (heavier) position. For dynamic balancing you need a balancing machine / transducers and a measuring system (say a FFT analyser). For a propshaft I guess the dynamic balancing option would be best.

Even so I think you need to see if it is a propshaft problem first - before you head off trying to find someone who can balance it.

If you are brave enough to drive the car - fix / tape a video camera or cheap digital camera (that will make movies) to the underside of the car and record the movement of the propshaft.

What ever you do look for a cheap fix first - don't get too worried about expensive fixes just yet!

S-Class Guru · #6 08-23-2010, 01:17 PM

I believe alll the 300 SE's from '88-'91 had markings on both shafts that identified where to interface them. One shaft had an embossed arrow, and the other had two arrows spaced a bit apart. Just center the one arrow between the other two, and you have the correct splines aligned. Assuming the shafts you have are matched and balanced this way to begin with - a rebuilt and re-balanced shaft set may not be, but should be if a good shop did the rebuild.

DG

david s poole · #7 08-23-2010, 01:39 PM

if it all started with the flex disc installation then that is where the problem is.you need to put car up on rack with engine running and in drive ,look very carefully at the disc behind trans and make sure that it's turning in a perfect circle with no runout.for ex.get a large screwdriver and hold the blade close to flex disc while the drive shaft is turning and see that the distance stays the same as the disc goes around.i'm betting it doesn't.

macdrone · #8 08-23-2010, 06:39 PM

I am not sure of the year of your MB but Also with the flex disc is the carrier bearing. If he pulled the bearing it would do that every single time due to the weight. I would think the shaft wasnt balanced if it was that bad. Also the flex disks maybe incorrect for the vehicle. If he got it with larger holes or didnt make sure the spacers were in it could cause all that vibration.

Like everyone has said here go back to the original problem. Its most likely there.

Like if he changed motor mount or something and you have a decent missed it would feel crazy.

mak · #9 08-23-2010, 07:07 PM

The flex Disc has a marking for the correct installation.Its in German indicating the transmission side of the flex disc .
nak
300se

boem · #10 08-24-2010, 09:52 AM

Thank you all for helping with this issue, all rivers flow to the sea, you all support what I belive the problem is.

Meanwhile i had found out that the passanger side mottor mount is faulty, do any of you think that it can be the issue? should I replace it before doing anything else?

Anyone have any idea where to get an affordable manual for this vehicle??

Stretch · #11 08-24-2010, 01:01 PM

My advice is to do as much investigative work as possible before moving on to another area of the car. Your terminology "faulty" brings lots of different ideas into my head - many of which would probably confuse the issue!

Do some cheap snooping around your car and come back here with what you've found - for example:-

"when I pull down on my prop shaft I"...

or

"I've noticed that those funny marks on the flex discs are"...

david s poole · #12 08-24-2010, 01:38 PM

i very much doubt that a crushed or broken motor mount will cause the vibration.check the runout on the trans flex disc.

Ferdman · #13 08-25-2010, 05:27 AM

boem, agree that the bad motor mount shouldn't contribute to the vibration, but replace both motor mounts so as not to cause other problems. Have you determined that the driveshaft halves are assembled properly, i.e. that the match marks are aligned?

macdrone · #14 08-25-2010, 08:03 PM

Motor mount can cause bad vibration but if it happened when the shaft was messed with I would stay with that.

boem · #15 08-26-2010, 12:39 PM

Just ordered new pair of motor mounts. Will replace those. Looking for a mechanic willing to work together on this issue, I don't have a lift, Will test for allignment of two part drive shaft, runout of flex disk.

If anyone have more suggestions it would be greatly appreciated.

Meanwhile, In return anyone need advise with irrigation, landscaping or home improvement please do not hesitate, will be happy to help.