W202 unsolvable driveline vibration

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Rusty220

Member
Joined
May 13, 2022
Messages
48
Location
Brittany FR
Car
1997 C250 TD
Hello everyone!

I am trying to get rid of a driveline vibration, i'll try to explain as best as i can what happens but this is really doing my head in. I bought the car about a year ago and swapped the motor mounts and front flex disc as they were decimated (Lemförder mounts, SGF flex discs). Put a set of new Goodyear tyres too. Got a few months of smooth driving out of it. At some point i thought it wasn't driving as smooth as it should and there was some kind of vibration coming from underneat the car or at the back.

Decided to give the car a good inspection and replaced the trans mount with one from Febi and realised that the rubber was collapsed around the the propshaft carrier bearing causing the driveshaft to move about when taking off. About a month ago i've replaced the carrier bearing/bushing with a Febi unit as well as the rear flex disc while everything is apart. Now i have this vibration which is very pronounced around 80-100 kmh (50-60 mph?). It's not a vibration that shakes the car but something that can be felt and heard, like a rumble, sounds kind of like i'm driving with an open window. Extremely annoying.

This whirring vibration is not influenced by cornering and is the same under load or coasting or in neutral, only speed dependent

Observations:

- Both halves of the propshaft are aligned according to factory marks. It was off by one spline which i thought was the cause of the vibration, we took it apart again and put it back together as it should but it did almost nothing.
- All the balancing weights are still welded on the driveshafts.
- Slight play in the splines but none it the u-joint, whiched moved freely if i recall.
- Slight play in the gearbox output bearing.
- No play in the diff pinion bearing.
- Slight play in differential CV axle bearings but not a drop of oil leaking.
- Can't make the CV axles clunk with wheel on or off the ground.
- Front vibration damper in good shape.
- Differential mounts are old but ok, no play at all there.

What i've tried to no avail:

- Rotated and balanced wheels many times, no issues there.
- Unbolted the engine mounts, trans mount, exhaust hanger, carrier and rolled the car back and forth a few time.
- Tried changing the angle of the driveshaft by installing various thicknesses of washers under the carrier.

This is driving me absolutely mad to the point of thinking about getting rid of the car despite all the other work i've done to it. The car is a 97 W202 C250 TD manual, 385000 km on the clock.
 
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Can you ascertain the frequency of the vibration? Eg, the same as road wheel rotation? (drive line would be some three times higher).

No mention of wheel bearings... They can create noise (before exhibiting play) but maybe not a tangible vibration.
 
Can you ascertain the frequency of the vibration? Eg, the same as road wheel rotation? (drive line would be some three times higher).

No mention of wheel bearings... They can create noise (before exhibiting play) but maybe not a tangible vibration.
It's hard to tell but to me it feels more like it is propshaft related, it feels like it matches engine rpm in 4th gear (4th gear ratio is 1:1 i believe).
 
It's hard to tell but to me it feels more like it is propshaft related, it feels like it matches engine rpm in 4th gear (4th gear ratio is 1:1 i believe).
Which does imply aft of the gearbox - but you've checked about everything there there is to check.
Odd, that it doesn't change with load if drivetrain related.
Is there any possibility of it being something loose being excited by air flow - eg an unsecured corner of an undertray - that sort of thing?

I once had an annoying rattle in my smart - but only at idle. After extensive investigation of the drivetrain, mounts, etc, etc it was found to be the warning triangle behind the passenger seat rattling in its hard plastic box...
 
Which does imply aft of the gearbox - but you've checked about everything there there is to check.
Odd, that it doesn't change with load if drivetrain related.
Is there any possibility of it being something loose being excited by air flow - eg an unsecured corner of an undertray - that sort of thing?

I once had an annoying rattle in my smart - but only at idle. After extensive investigation of the drivetrain, mounts, etc, etc it was found to be the warning triangle behind the passenger seat rattling in its hard plastic box...
Didn't mention it but i've tried driving with the plastic undertrays on and off the car as well! I can feel the vibration in the armrest and seats, about the 80-100 kmh is the worst and it doesn't get worse the faster i go, it may even be slightly smoother at say 130-140 kmh.
 
I can feel the vibration in the armrest and seats,
Can often be rear wheel related but looks like you've addressed this already. What about a buckled wheel? Or rear suspension mounts?
 
Can often be rear wheel related but looks like you've addressed this already. What about a buckled wheel? Or rear suspension mounts?
The wheels look perfect and i have inspected them a few times alreay. A mechanic told be it could be a wheel bearing and to be honest there's a lot of road noise in the cabin, something that could be a wheel bearing but i can't imagine a bearing making this kind of rumble that feels like an open window. It definitely became worse after the work done to the driveline.
 
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Wheel bearings can be deceptive and hard to pinpoint. I've had them noisy when driving but quiet when spun by hand with no play. Then without warning a horrific noise (in one instance I thought a RAF fighter was overhead) which went as quickly as it came and only then was it noisy when spun by hand. Usually though, they can be provoked to change their noise under braking (eg light application of brake while still on-throttle).
 
I had a car with similar issues. Turned out to be the rear rubber donut on the prop shaft was worn. Since your car is on mega miles that would be my hunch
 
Hi, I have a Range Rover sport that I replaced rear propshaft due to collapsed center bearing rubber, after a road test I had a very very slight noise vibey type sensation that I couldn't make my mind up where from, obvious conclusion was prop balance, it gradually got more noticeable at first slight pressure on the steering to the right which then made me think possible ps pump, that sort of noise and feeling in steering wheel, dont get me wrong this was very slight but you know your vehicle you know when something is not right. It progerssed abit more and is the front o/s wheel bearing.
So is your vibe gradually getting more pronounced as you used it.
Another thing to check is tyres, I've drove cars with noise and vibes and found its been a tyre that looks perfectly good, maybe worth swapping each wheel individually with a spare to eliminate the possibility of a tyre or as whitenemesis mentioned a possible buckle.
 
Run the car up on a ramp with the wheels off the ground at 50mph, it should become obvious where it's from when you can see it!

+1 on the tyre. I had a car with this symptom, the internal structure of the tyre had failed and it was causing a vibration that could not be tracked down easily.
 
I had a car with similar issues. Turned out to be the rear rubber donut on the prop shaft was worn. Since your car is on mega miles that would be my hunch
Thank you, i owe you a lot. You got me thinking about the flex disc and i think the new flex disc is not installed as it should. As i understand it, the propshaft turns clockwise looking towards the rear of the car. This means the propshaft "pushes" the thicker part of the flex disc. Mine is obviously installed incorrectly when i compare to internet pictures and youtube videos. It also means that the inserts are sticking out where they shouldn't and the flex disc is bent in 6 locations. This might be the end of the nightmare, i am going to install it as it should tomorrow with my mate!
 
Thank you, i owe you a lot. You got me thinking about the flex disc and i think the new flex disc is not installed as it should. As i understand it, the propshaft turns clockwise looking towards the rear of the car. This means the propshaft "pushes" the thicker part of the flex disc. Mine is obviously installed incorrectly when i compare to internet pictures and youtube videos. It also means that the inserts are sticking out where they shouldn't and the flex disc is bent in 6 locations. This might be the end of the nightmare, i am going to install it as it should tomorrow with my mate!

Fingers crossed. Please let us know if it worked 👍
 
I'll keep you posted for sure! I've seen hundreds of threads on various forums and no one ever made any mention of this. Fingers crossed.
 
Done! 80% of the vibration of the car is gone! The biggest issue i had to deal with is that the metal inserts were pushed the wrong way, tightening the bolts again with the flex disc correctly installed helped but the flex disc is still not 100% straight, hard to explain without a picture. I'll keep an eye on it and maybe buy a spare donut with all the hardware but it drives so good now, just had a stroll, driving with no reason, just enjoying the smoothness and the gruff 5 cylinder sound on this sunny day!.

Thanks everyone for your help. I'll keep you posted if something happens.
 
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So BLOODY OBVIOUS !......once explained :D I wonder how many vehicle out there are rolling around with the flexdisc in the wrong way around ? Lesson learned , certainly one to keep an eye on . result Rusty 👍
 

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