[rc05]

I recently purchased a '90 300SE w/82,000 miles. Very nice vehicle,, garaged and extremely clean.
Had the rumble from the beginning - thought it was the badly worn rear tires. Fronts were fairly new. Put the fronts on the rear and 2 new tires on the front. Still have the rumble.

My local garage, which specializes in import autos, believes it is the rear axles. According to them there is no play in the axles and that there should be a little. They did run the drivetrain while on a lift and they ruled out driveshaft or wheel bearings.

The rumble is most prominent at 45 mph whether accel. or decel. Is feelable mostly on decel. from higher speeds.

I have searched the issue on this forum and still have a few questions.

1. Is the rear axle the probable cause of the vib/rumble?

2. Is it feasible to replace the inner and outer boots and will this help? Would I be able to replace the boots or must the axles be removed?
Mechanically, I've done tune ups, fluids shocks, minor repair and a few more difficult jobs.

3. Is there a rebuild on the axles that can be done or is it necessary to replace them.

Any help appreciated. My first Benz - quite the driving machine.

Thank you, Ron

 

[markusfmeyer]

A few quick thoughts:

1) what is the service history? Has the diff fluid ever been changed? If not, or you don't know, might be a good time to do so.
2) did they check the flex disks at each end of the driveshaft for any cracks/stress marks?
3) are you sure its coming from the rear, not the front?
4) have you checked front wheel bearings?
5) have you checked to make sure no little leaks in the exhaust, that can sometimes cause a rumbling noise.

Is it a noise or a vibration feeling in the car itself?

 

[rc05]

Thanks markusfmeyer:

1. I do not have the service history, I do plan on changing the diff fluid next week. Had to order the hex bit socket.

2. Will have garage check flex discs.

3. 90% sure vibration is coming from rear.

4. When it was on rack running all wheel bearings were checked.

5. Exhaust is tight.

Definitely a vibration - most prominent at 45 mph at both accel and decel. Very feelable from higher speeds expecially on decel.

Thanks again, Ron

 

[markusfmeyer]

Next time it happens at 45mph or so, put the transmission in neutral and see if its still there or not, out of curiosity.

 

[284037]

^^
Yep, that's a good way to check. The problem could be the differential

 

[p100]

Replacing the rear axle boots would not do a thing. The boosts just protect the CV joints from dirt. Do you know if the axles on the car are the original axles, or are they rebuilt ones? You could have a pair of poorly rebuilt axles. These 126 axles are very difficult to replace the boots on as the CV joints are not removable and must be taken apart. There are some shady outfits that do this improperly.
I have heard complaints about cheap rebuilt axles causing problems such as you describe. This is why some parts houses do not even sell rebuilt axles. There is only a handful of companies that rebuild these axles properly.

I would also suspect the differential - you could have a bad pinion bearing for example.

Bad rear wheel bearings could conceivably cause a problem too.

Incidentally, where is the car being serviced? I am in Melbourne Florida, only about 50 miles from you.

 

[Teutone]

Nothing to add, but are you positive the car has only 82,000 miles on it?

 

[rc05]

Thank you for your responses.

markusfmeyer - I will try putting in neutral while at 45 mph and report back.

p100 - Thanks for the tips, especially about the rebuilt axles. I'm assuming the axles on the car are original. Presently I use Don's Import Auto Service in Vero Beach on 43rd.
Who do you use in Melbourne?? If interested, I would like to meet up and have a cup of coffee (or a hamburger at Smokey Bones!!). I'm semi-retired. Was in the foundry business for many years.

Teutone - yes, I did a car fax (NADA Auto Check). It's a Florida car - one owner from Miami. Based on the auto check and the condition of the car, I believe the mileage is correct. The car was apparently garaged. All rubber around the windows, trunk, and hood is like new and very pliable. There is absolutely no seat wear. Owner must have been a lightweight. Underneath is very clean as is under the hood. Under hood was not cleaned or sprayed with anything - in normal (a little dusty) condition. For 18 yrs. old, paint is beautiful. Very shiny black. Chrome (aluminum?) around all windows very clean - like new. Everything works. I couldn't believe it when I saw it. "Just had to have it".

 

[rc05]

I did change the differential fluid. Seemed to be better at 70 mph, however from 40 to 55 on both accel. and decel. rumble/vibration is still there. This is the range where it is most prominent. The old fluid was very dark (black) when I drained it.

markusfmeyer - I did try putting the trans in neutral while at 45 mph. Made no difference. What does this mean?

 

[mramay]

Two additional causes for vibrations:
Bad tranny mount. It causes a vibration in the driveline during acceleration. Can be seen above the steel crossmember at the rear of the tranny. Mine went bad and I thought it was a drive shaft problem.

Bad shock mounts on the rear shocks. Lots of thumping back there when the rubber doughnuts of top of the shocks get old and quit.

 

[rc05]

The problem turned out to be the Front Driveshaft Flex Plate and the Center Driveshaft Carrier support. Car is now very smooth. No vibration whatsoever. I saw the flex plate while it was on the lift. The rubber was all messed up and the plate turned within the bolts. The carrier support was also very deformed. Saw it after they changed it out.

One interesting note. My first garage never saw the defective flex plate. They concluded that the problem was the rear axles. The defective flex plate was very visible.
The second garage I went to does general work but specializes in transmissions and A/C. I was there for my daughters transmission problem. I asked the foreman iabout my vibration problem. He said some times the flex plate can cause that condition and he was right. Sometimes it pays to get a second opinion.

Thanks for your responses to my post.

 

[a3jeroen]

Thanks for reporting back. This might help someone else in the future.

gr J

 

[wbain]

In addition to your driveshaft mount and flexdiscs, make sure the engine and transmounts haven't collapsed, as well as the differential mount. The driveshaft isl supposed to be aligned and the flex discs not under any type of load.

 

[rc05]

Thanks wbain. That's a good point. I will get them checked out soon.

 

[rapcat]

Hey I'm from Melbourne too P100 PM sent !
I just accrued a 87 420SEL two days ago and sounds like I have the same type of problem. If not worse
The seller told me that it has a bad tire but they all look decent... It makes a load tire like noise from the wheel and also nasty vibration from take off to around 20mph. The car does drive straight. Please help me get this thing on the road safely.

 

[bosanci28]

The problem turned out to be the Front Driveshaft Flex Plate and the Center Driveshaft Carrier support. Car is now very smooth. No vibration whatsoever. I saw the flex plate while it was on the lift. The rubber was all messed up and the plate turned within the bolts. The carrier support was also very deformed. Saw it after they changed it out.

One interesting note. My first garage never saw the defective flex plate. They concluded that the problem was the rear axles. The defective flex plate was very visible.
The second garage I went to does general work but specializes in transmissions and A/C. I was there for my daughters transmission problem. I asked the foreman iabout my vibration problem. He said some times the flex plate can cause that condition and he was right. Sometimes it pays to get a second opinion.

Thanks for your responses to my post.

can you tell me where exactly are located the "Front Driveshaft Flex Plate and the Center Driveshaft Carrier support. "" any pic,, i have the same proablem!

i buyed the car and i had it for 1 year in my backyard,, and when start the motor and drove it on the freeway for the first time,,man at 45 it start sheking like hell ,,so i hade to take the first exit out,, next day i put new tires in front,,but is stll does at 65 to 80 not much but i can still fill the vibration,,but not like before...

and i did not try in neutral to see but i will do it,,,
and i think i have the same issue,,,like you so please can you make a pic or some to see what exactly you changed,,
thanks

sorry for my english

 

[Teutone]

can you tell me where exactly are located the "Front Driveshaft Flex Plate and the Center Driveshaft Carrier support. "" any pic,, i have the same proablem!

i buyed the car and i had it for 1 year in my backyard,, and when start the motor and drove it on the freeway for the first time,,man at 45 it start sheking like hell ,,so i hade to take the first exit out,, next day i put new tires in front,,but is stll does at 65 to 80 not much but i can still fill the vibration,,but not like before...

and i did not try in neutral to see but i will do it,,,
and i think i have the same issue,,,like you so please can you make a pic or some to see what exactly you changed,,


thanks

sorry for my english

The Mercedes Benz service CD's (see sticky for listing of the service files) has little info on anything transmission related.
One of the DIY / FAQ stickies on top has a transmission file.
Have you tried a forum search with 'replace transmission mount' (or differential mount).
If you are not sure how, please read the "Welcome to the Forum' announcement / tutorial sticky on top of the W126 page Benzworld.org - Mercedes Benz Discussion Forum - Announcements in Forum : W126 S,SE,SEC,SEL,SD,SDL Class
Cheers

 

[rc05]

bosanci28:

I had the front flex plate replaced which is located at the front of the driveshaft. It is a round hard rubber plate that is about 5" od, 1 1/2" id, 1" thick and has six steel sleeves with 3/8" holes for bolts.
The carrier is about 3 3/4" od, 2" id, and 1" thick. I believe it is located at the center of the driveshaft. It has a flange with 2 holes for mounting bolts.

There was absolutely no change in the vibration when I was moving and placing the shifter into neutral.

Hope this helps.

 

[bosanci28]

bosanci28:

I had the front flex plate replaced which is located at the front of the driveshaft. It is a round hard rubber plate that is about 5" od, 1 1/2" id, 1" thick and has six steel sleeves with 3/8" holes for bolts.
The carrier is about 3 3/4" od, 2" id, and 1" thick. I believe it is located at the center of the driveshaft. It has a flange with 2 holes for mounting bolts.

There was absolutely no change in the vibration when I was moving and placing the shifter into neutral.

Hope this helps.

ok,
because i know that at the trany there is a flex plate , then you have the bering at the drive shaft (at half way) and the flex plate at rear ,,
i only check to see if the bering at half way it has little play,,

but it my be for the rear tires also?,,they not so good,,i put them from the front to rear and i hade the proablem at 45 miles /p/hr with them,, not that i moved them to rear maybe ,now the rear is doing the shecki at 65-80,, proably i need some good tires,,

when im on the freeway and i have 70/m/hr and if i let the gas pedal down the car stops doing that,,but some time it does it,, it looks when i put load on the shaft,,i need to check to see if it does in neutral,

thanks

 

[bosanci28]

proablem solved!
the wheel from driver side rear ,,had no Weights,,the balance of the wheel was the proablem...
runs okay now
thanks