Throbbing/Rythmic Vibrations at 40-65 MPH - Page 2 - PeachParts Mercedes-Benz Forum

obwielnls · #16 03-12-2008, 02:43 PM

Quote:

Originally Posted by legasea

I have this low level throbbing/rhythmic vibration when I am going about 40 - 65MPH. It is more like a humming than vibrating that comes and goes in rhythm at said MPH. I checked the flex discs and motor mounts yesterday which appear to have already been replaced at some point. What would the next thing to check? I have read about other culprits (centerline bearing/support, motor shocks, tranny mounts, bad axles and wheel bearings).

I am not certain where the tranny mounts are located and how to tell if the motor shocks are bad. My guess would be a bad centerline bearing/support or the wheel bearings. But I guess both of these just need to be replaced to find out if they are bad. Any thoughts or advice for troubleshooting on my own before bringing it in for service?

I can't tell what kind of car you have, however, I had a 88 300E, W124 that did this. There is a bulletin on it. The drive shaft is actually out of balance. Likely someone replaced some parts and didn't reassemble it correctly.

legasea · #17 03-12-2008, 05:12 PM

Quote:

Originally Posted by obwielnls

I can't tell what kind of car you have, however, I had a 88 300E, W124 that did this. There is a bulletin on it. The drive shaft is actually out of balance. Likely someone replaced some parts and didn't reassemble it correctly.

I have an 83 300D Turbo.

I was actually thinking the same thing today. Is it possible for a mechanic, or myself, to disassemble and rebalance? How does one gauge that and determine the correct balance? A machine?

Thanks

winmutt · #18 03-12-2008, 05:24 PM

W123 DS will not come unbalanced.

kernelpanic · #19 03-13-2008, 06:27 AM

Quote:

Originally Posted by rrgrassi

Check the center support bearing and bushing. I had a truck that did this, but it was never diagnosed or found. Never had a failure either.

I 100% agree...I had the same problem and replaced the center support bearing. Problem solved!
Only about 1 Hr of my time to replace it

leathermang · #20 03-15-2008, 01:17 PM

Remember to mark with paint all the parts in the driveline which might be able to be put back together in a place different from where they started out....

JackG · #21 03-15-2008, 06:23 PM

I have a vibration that starts about 22mph and last to about 30 mph.
Not in the wheels, but feels more like it's in the rear......kinda a seat of your pants vibration........same thing?

legasea · #22 03-15-2008, 06:48 PM

Quote:

Originally Posted by JackG

I have a vibration that starts about 22mph and last to about 30 mph.
Not in the wheels, but feels more like it's in the rear......kinda a seat of your pants vibration........same thing?

Yes, my vibration happens at higher speeds, but its not just a steady vibration, it is rhythmic, meaning that is constant cycle of heavier vibration to softer vibration. sounds like someone is moaning louder and softer. I believe my issue is in fact in the centerline bearing. makes sense.

tgblanken · #23 03-15-2008, 07:04 PM

I have the same vibration. I replaced the center support and bearing. It did not fix the problem.

legasea · #24 03-15-2008, 07:55 PM

Quote:

Originally Posted by tgblanken

I have the same vibration. I replaced the center support and bearing. It did not fix the problem.

What is your next step? Have you replaced anything else already?
Engine mounts? Tranny mounts? Flex Disks? Wheel Bearings?

These are all items I have in mind and some of these items look like they have already been replaced by a previous owner. I suppose it could be an axle or possibly even an unbalanced driveshaft. I have heard contradicting theories on the driveshaft. Some say it is impossible for it to become unbalanced....then why, I ask, is it so important to make sure it is put back on the same way it came off? Some say to mark the driveshaft so it is easier to put back together. This leads me to believe if someone else has removed the driveshaft and put it back on the wrong way, it could become unbalanced and therefore create a vibration. Question is, how does one tell if a driveshaft is unbalanced and how does one rebalance it?

tgblanken · #25 03-15-2008, 09:11 PM

The flex disks are in good shape. I really haven't thought of my next step. I would like to fix it but don't want to spend big dollars to have the drive shaft balanced.

seth411 · #26 04-10-2008, 04:39 AM

Has either of you guys fixed this yet? I'd really like to solve this. Mine seems to happen more when going up hill. I've recently replaced the engine and transmission mounts. It didn't make a difference.
Thanks

tgblanken · #27 04-10-2008, 11:42 AM

Sorry, I have not done anything with the vibration. I been tied up with kids activites and spring yard work.

RoysVeggy · #28 06-10-2008, 08:58 AM

TGblanken, I seem to have the same problem, but its only really bad with weight in the rear. I took a trip to Miami, and had 3 adults in the back. On the way back home (70-75 mph highway speeds), that same sound you described started (it is rhythmic, meaning that is constant cycle of heavier vibration to softer vibration. sounds like someone is moaning louder and softer.)

After reading through MANY different threads, do you think I should start off replacing the Center Support Bearing? I checked ********az and they have a really good price on it.

My car just hit 299k, and runs like a top, especially with just myself in the car. Should I order multiple parts and just start replacing one at a time? Could the axles with worn CV boots have anything to do with the problem? Thanks again!

Mercury · #29 06-10-2008, 10:08 AM

It is possible for the driveshaft to become unbalanced, if one of the weights comes off. The more likely candidate is that the u-joint has become notched. The notch in the joint is very hard to feel by hand. This will give you the feeling of an out of balance. The U is a pressed in piece and is not user serviced. A high quality driveshaft shop can balance a MB shaft, but these are few and far between. Pressing in a new piece will cause a nice shaft to be out of balance Better off buying a new (rebuilt) driveshaft. It comes with a carrier bearing, and is not terribly expensive.

The MB shaft of this era comes apart just in front of the carrier, at the nut mentioned in previous posts. This is a splined piece, that if put back together one spline off will cause a true unbalance. The shaft is balanced and weighted as a unit. If you are taking apart the shaft, take a piece of tape along the axis across the spline (across the nut) and then some spray paint on the tape in order to get a nice sharp line. It is imperative to replace at the exact spline.