W124 - Dealing with the vibrations

It looks like my journey with the vibration and sound may not conclude just yet. There is a distinct noise that comes up when the transmission is in D and it comes up at about 1800rpm. I have no clue at the moment what this is. When the car is Neutral and revved to 1800 - 2500, this issue is not seen. So that concludes that this only happens when the car is in drive and has something to do with the transmission/drivetrain. The strange thing is, as I work on refreshing old and worn-out parts, all of these symptoms are coming up. I remember when the rear absorbers (link: here) were replaced, the ball joint bush went faulty a few hours later that prompted an Adhoc fix. Could there be a link with regards to the changes in dynamic of the ride height, flexibility, movement against the drivetrain that is bringing all these noises out? Strangely, I did put a hot tip on changing some new parts that would potentially introduce new noises.

When driving at 80km/h, there is a particular vibration that only hits the steering. Despite all attempts to diagnose what it is, I could not figure it out. I did go under the car with the engine running to check what could be the issue and noticed some noise being generated from the flywheel/torque converter area. Unsure why it is making that noise or if that is normal.

I made a video to record the said noise here.

There have been some suggestions on the vibration issue which are:

Check the alignment of the transmission mounting to ensure that left and the right side is evenly aligned
Torque converter may not be mounted dead center
Propeller shaft bearing

The power steering pump is also leaking and while the gasket has been replaced, it has not solved the problem. This will be checked and the worst outcome could be a replacement pump or complete rebuild and replacement of all seals in the pump.

I have made an appointment to have it checked, will update the outcome soon.

Update #1:

Took the car to the mechanic to have the symptoms checked. It wasn't a day with fewer problems:

The rear differential was humming
The rear axle shafts may need replacement if they are causing vibration
The exhaust is leaking at the joints due to poor welds in the past

To sort this out, I will need to scout for a well-used differential, potentially one from Japan. And also the axle shafts also to have them properly fitted to ensure that the fitting is proper and also hopefully no more vibrations. As that will mark, every component of the drivetrain has been repaired or replaced.

It will be a waste of time or money to have the exhaust patched up, the pipes are old, and fixing one spot will just cause the next weak spot to leak. I will have this replaced with stainless steel piping when the funds allow it.

At this point, I am a little demotivated and dejected. The journey gets a few steps longer just when I thought the end is in sight.

Update #2:

I have posted my issue on a forum to get some pointers on what could be the issue, one of the replies was pointing to the propeller shaft bearing because when the propeller shaft was replaced, we did not have a new bearing and the bearing from the old propeller shaft was carefully pried out and reinstalled into the replacement shaft. The bearing in the subject is a few months old. I am of the opinion that the bearing would have fit in like gloves in the previous propeller shaft and may not be a fit now. But if that was the case, the noise should not have come up now, which is after the bushing and mounting replacement.

But to allow this issue to further diagnose, I found a video on YouTube that has a very similar sound to the issue that I have, the video can be seen here.

I was then browsing around and found a post with prominent mechanics being featured in a post and decided to call one of them.

After sharing the issue, to the best that I can, he said, he will need to drive to know the sound. But he also thinks that the issue may not be the bearing but rather the universal joint at the center of the propeller shaft. Again it's inconclusive presently.

When asked about the steering vibration, he says the issue could either be a work wheel knuckle as I had issues in the past, or a steering box coupling since it only affects the steering.

Now with this new hypothesis, we are unsure if the initial suspect of a faulty differential and driveshaft is still the issue.

Update #3:

Rhino was at a workshop for a second opinion on the vibration, there has not been a concrete suspect but a few things were done to confirm the suspicion:

Swap all 4 wheels from a car that does not have this issue - this will remove the wheels from being the issue
Replaced the steering drag link from FRAP to Mercedes genuine (made by TRW) since there is no confirmation on the FRAP brand quality - did not solve the issue as this was not a faulty part
Jacked the rear left wheel and drive up to 80 kmh to feel the vibration, next, repeat the procedure with the right wheel. Now, this lead to a new observation, the left side vibrated more compared to the right side - the axle shaft is not vibrating symmetrically and is the focus of inspection.

A loaner axle shaft was not available to be tested and hence we could not confirm this theory, but this procedure definitely removed the entire front steering system (including steering box coupling and knuckle) and also the propeller shaft from the equation, leaving the focus to be specific to the rear. Another observation was found that the axle shaft is not firmly attached and can move left and right, causing shimmy. The differential does not cause vibration but will also be checked.

We are making baby steps forward and I hope the issue is nailed soon.

Update #4:

While the car was at the mechanic to sort an engine leak (detailed here), I have requested the mechanic to remove the present long-shaft from the car and have the old one (which is not balanced) installed. I did this to allow the replacement long-shaft to be balanced in order to eliminate any sort of long-shaft balancing issue.

I am preparing work for the next upcoming work where the long-shaft will be fitted with new bearings, bearing boot, and also centering bushes on both ends of the long-shaft. I am also scouting for a well-used axle (of ratio 3.06, which came with the car and validated to be for the E280 AT). The work will also include replacing the rear driveshafts.

After replacing the old long-shaft, the vibration got worse and was rough. Now, this confirms that the long-shaft was indeed better, but to have it balanced will confirm that it is straight.

Also, after the car rested overnight, there was an observation that the earlier reported noise that was generated (reported at the beginning of this post) specifically when the car reaches 60 kmh is a lot milder than it is. Now the only variation to the setup is the replaced long-shaft. I have suspected earlier that the recycled bearing, albeit a few months (and a few thousand km) old is the culprit.

But in a quest to have this properly corrected leaving no loose ends, I managed to locate an engineering shop that could repair and balance the long-shaft. Since this long-shaft came off a used scrap car from Japan, it should be in good condition, but since the vibration is not solved and it involves a component from the drive train, I want to have it addressed.

I got lucky today, after the first cold call I made did not yield any results, the second one was succesaful. A brief conversation later, the workshop confirmed that they can balance and repair the long-shaft, I made an appointment to send the long-shaft in to have it balanced. So as we speak, the long-shaft has been admitted to the engineering shop and is due for the next few days. I have also placed an order for a set of brand new and genuine rear axle shafts, hard to come by and definitely not cheap. The only missing link was a rear axle that has been located at the correct ratio of 3.06.

So the completion of the drive train is now pending my overseas purchase to be delivered that contains all the necessary bearings, boot, coupling, centering bushes, and the charcoal can.

Update #5:

The machine shop called to informed that the long-shaft was fine and it was straight, there was no adjustment to be made. I took this opportunity to also have the CV joint replaced.

Update #6:

With the installation of the repaired long-shaft, replacement axle, new flex discs, centering bushes for the long-shaft, long-shaft center bearing and axle shafts, the vibration has not been resolved.

Driving at different speed now shows that the vibration has got worse. Not only that, but the replacement axle was also humming despite initial checks.

The axle will need to be replaced by the used parts dealer, long-shaft will need to be checked as well for faults.

While the replacement axle will be delivered and installed, I have sent the old long-shaft that I had for balancing in a different shop that specialises in long-shaft repair and building.

The long-shaft shop assessed the long-shaft and later informed that the shaft was a little out of alignment. They also updated that the old center has worn out, possibly because the shaft was not true and overtime, it would have destroyed the bearing.

The old long-shaft has been repaired and needs a new center bearing before installation.

Update #7:

To begin with the replacement axle was not a fit, the other axle that was used was also not in god shape, when the temporary axle was removed, the week old axle oil was murky. With no choice in hand, we re-used the old axle.

I got a tip on a tranny in one of the chop shops that was imported from Japan, and belong to a W124 E280. After having it assessed, the tranny was purchased and delivered to the workshop.

The replacement tranny was then checked and the usuals were done, which includes new filter, seals, oil seals and even the torque converter seal. The tranny came with its torque converter that was fitted. It was completed with filling of fully synthetic Revenol ATF.

All of that work made the car smooth, a whole lot from where it was before this.

The next piece of work was alignment and balancing of the tires and I found someone who knows the W124 well. He did his magic and spotted a few issues that was not picked up earlier such as the wheel center bore was 0.5mm larger than the hub, the tires that I have, which is the Michelin XM2+ are hard compound tires, which means it will transfer more vibrations to the absorbers. This can be remediated by replacing the rubbers with on of a softer compound. The trade off will be a lesser service life in terms of mileage.

The hunt continues, but this item will take a break until there is more indication of where the problem could be.

Update #8:

There is a minor observation made on the front right wheel. While it is not conclusive, there seem to be some resistance when the hub is being turned while the wheel is off. This issue is not the brakes as if it was, the resistance will be felt at the same spot, but in this case, it is not.

A quick call to the mechanic revealed that it could be the front wheel bearing that could have been defective when it was installed. He did ask me to drive it for a bit to see if it improves and it if doesn't, we will have it replaced. The said bearings were not too old, when it was fitted a few months ago. I documented the issue here.

An appointment with the mechanic revealed that the old bearing has seized and needed to be roughed out. New bearing was duly installed. We also got the steering damper replaced as well.

Initial impression, smoother but the vibration was still there.

Update #9:

Being sick and tired of the vibration prompted me to look for opinions. I was referred to another independent garage that works on Mercedes.

An appointment was made and the mechanic said he needed time to diagnose, to which I agreed. I sent the car in at Noon and at 2:00pm the same day, the narrowed down on the issue.

The issue seem to be a the axle shafts that is vibrating in motion in its axis. This would either be a faulty axle shaft, which was purchased new or a faulty axle.

Further investigation revealed that the axle also had a rather prominent freeplay. This indicates that the inner of the axle would have damaged or worn out.

More investigation is being done, I am hopeful that the end is near for this vibration issue.

Update #10:

I got Rhino back. The vibration has tremendously reduced but not gone.

One of the two drive shafts was not straight and that was causing the vibration in motion. The faulty piece was replaced.

The axle is definitely faulty and needs to be replaced. However, with the engine being a 2.8 engine, with ABS and no ASR and no ASD, this model is not too popular and scouting for a correct a little more challenging.

I am keeping a lookout for an axle for replacement and will not be driving much until it is replaced to avoid any further damage to the axle shafts, propshaft or even the transmission.

Update #11 - Final:

Finally after 5 months of dealing with the vibrations, this will be the last entry to this issue. The axle was sourced and replaced. A mechanic managed to scout the correct 3.06 ratio axle with ABS and without ASR and ASD.

The sourcing of the part took some time, and I transferred the risk to the mechanic by getting them to source it. Without which, if the axle is faulty and installed, I will have to bear the installation changes.

The installation took a few hours.

Initial observation, the vibration on the steering is no more there. There is some between 65 to 90kmh, but that could be tires or longshaft and it is too minor for me to lose sleep over. When it gets worse, then I will sort it out accordingly.

Shifting of gears is much smoother now, which is because there is less freeplay.

All in all, this adventure of 5 month finally concluded, it was not a straight road to sort this because there were a number of issues and all of them resulted in vibrations of some sort.

With this, the vibration issue has been dealt with.

Pictures and videos:

The rear differential is suspected to have worn out

Differential with ratio 3.06

The strange wheezing sound that is being isolated - resolved, this was caused by bad long-shaft center bearing

A similar issue with similar noise found on YouTube - resolved, caused by bad long-shaft bearing

Propeller shaft universal joint - this picture was taken from the internet, the one on W124 do not have clips and will have to be properly welded to avoid balance issues