Center Support Bearing Diagnosis

[JHZR2]

My 2008 ML320 CDI has 205k miles.

I think the center support bearing is failing on it. I took the vehicle about 200 miles yesterday, at around 99 miles, just before my halfway point that we turned around, I started to get a grinding noise. It came out out of nowhere while we were just slowly going down a local highway.

Of course I checked underneath, thinking it was maybe a grinding brake or something like that, but there was no sign of anything dragging or anything else.

I start to hear it around 25-40 mph, and on the interstate at 65+ there’s enough road noise that you don’t hear it much.

I ran alongside the vehicle while my wife drove, and then rode in the back. No signs at all of brakes dragging. No heat. It seems most noticeable right on the floor hump where the driveshaft is. Can’t hear it from outside of the vehicle.

Here’s an around town video:



It sounds a lot worse in the video than it does in the car. It sounds kind of like a grinding brake in the car. I noticed as we listened more critically, that it would transmit the sound of the transmission downshifting while coming to a stop.

At 35s you can hear how it randomly changes for no reason.

At 2:10-2:15 you head the sound change due to downshift.

The vehicle runs perfectly, drive smoothly, shifts perfect, and breaks perfectly. I don’t think there’s any other issue, and I don’t know that there’s anything else like a severe low fluid condition, as I changed all fluids in the summer.

I have to think maybe it’s a center support bearing where the bearing itself is failing? Thoughts?

 

[GMBoy]

Have not dealt with the center bearing on your particular model but the Cadillac CTS 2003-2013 are notorious for the center bearing to go out and you have to replace the driveshaft as the center support is not servicable and NO driveshaft shops near me will replace it alone. The way it is designed doesn't allow it to be rebuilt. Now I did buy center support assy off ebay and tried it myself on my on 2008 CTS and it was a pain and lasted less than a year which then I just replaced the driveshaft with a brand new one since every one I got from LKQ was already bad. Any CTS that comes in my shop for this gets a new driveshaft. As the CB got worse it would finally be very noticable when leaving a stop as the drive shaft would binf and release and sound like it was hitting the floor board.

Now that I typed a lot of nonsense to your situation - you won't know until you look under there then see if is is repairable or if driveshaft replacement is the only way. Good luck.

 

[JHZR2]

Have not dealt with the center bearing on your particular model but the Cadillac CTS 2003-2013 are notorious for the center bearing to go out and you have to replace the driveshaft as the center support is not servicable and NO driveshaft shops near me will replace it alone. The way it is designed doesn't allow it to be rebuilt. Now I did buy center support assy off ebay and tried it myself on my on 2008 CTS and it was a pain and lasted less than a year which then I just replaced the driveshaft with a brand new one since every one I got from LKQ was already bad. Any CTS that comes in my shop for this gets a new driveshaft. As the CB got worse it would finally be very noticable when leaving a stop as the drive shaft would binf and release and sound like it was hitting the floor board.

Now that I typed a lot of nonsense to your situation - you won't know until you look under there then see if is is repairable or if driveshaft replacement is the only way. Good luck.

all my older MB driveshafts are rebuildable. The CSB is sold as a replaceable part. They’re designed to run the driveshaft straight, there are u joints in them to take up differences, but they aren’t really there for angles.

Regardless, for this vehicle, yes, I see a $1700 driveshaft, or a $68 aftermarket bearing. It looks the same job as any other, mark the shaft, pull apart, remove bearing, press on, install.

Question though is what is the noise??!?

 

[GMBoy]

Sounds like U joint noise from what I can faintly hear

 

[Kira]

Whatever you do, don't four grand that puppy down the highway without a fire extinguisher and a first aid kit.

 

[GON]

Assuming your MB has flex disks, have the flex disks been replaced?

I replaced flex disks and the center driveshaft support bearing on a w220 some years ago, in my driveway under jackstands to solve a like noise.

 

[SC Maintenance]

Hard to hear, but if it changes on a downshift its not likely the hanger bearing because its speed will remain constant - same as the diff.

Having said that at 200K if serviceable might be worth taking out and looking at. Once out you should know right away.

 

[JHZR2]

Hard to hear, but if it changes on a downshift its not likely the hanger bearing because its speed will remain constant - same as the diff.

Having said that at 200K if serviceable might be worth taking out and looking at. Once out you should know right away.

The only thing that video has in its audio is the noise. The vehicle gets very little engine noise through. That’s why this is so obvious. The phone recording amplifies it too making it sound worse than in real life.

 

[JHZR2]

Whatever you do, don't four grand that puppy down the highway without a fire extinguisher and a first aid kit.

I’m sure this isn’t the first vehicle with a bad support bearing.

 

[SC Maintenance]

The only thing that video has in its audio is the noise. The vehicle gets very little engine noise through. That’s why this is so obvious. The phone recording amplifies it too making it sound worse than in real life.

Well I can't tell at 2:14 whether the higher revs is just the engine or the scraping noise as well. I will acknowledge that 30 years wondering every factory imaginable has left my hearing less than perfect.

If it changes frequency with the downshift then its not likely that bearing.

 

[CleanSump]

I had a bad support bearing on a 300D. If you can get underneath you can check to see of it is loose or the rubber support itself is cracked or uber soft. Shake the driveshaft up and down, left to right to see if the bearing has obvious wear. Also. if the transmission is in neutral, you can do the typical u-joint check. The u-joint in the center of the driveshaft does wear out.
The Guibos on the ends of the shaft should be changed if you're dropping the driveshaft to replace the center bearing. Replace the mount if replacing the bearing because rubber doesn't last forever. Be sure to mark the driveshaft sections so you get it put back together the same as it came apart or you may have balance issues.
Edit: Note the center u-joint is not supposed to be serviceable. It is staked in place. Some driveshaft companies can replace it for you or you can buy a driveshaft with a replaceable u-joint.

 

[RooflessVW]

Unbolt the support from the car and you should be able to lower it enough to get some rotation to check it. Mark the hangar before removal because some cars have a preload spec.

 

[JHZR2]

Well I can't tell at 2:14 whether the higher revs is just the engine or the scraping noise as well. I will acknowledge that 30 years wondering every factory imaginable has left my hearing less than perfect.

If it changes frequency with the downshift then its not likely that bearing.

Agree it’s hard to tell. The final downshift to first always makes a noise. I’m confident it’s not a transmission noise, and I’m not sure the frequency changes, I think it’s just transferred/transmitted noise. The transmission shifts perfectly; up and down. I would think that if the issue came from there, I’d hear it further up, and shifting would be a bigger deal. Unless it’s something like a fluid pump (?).

 

[Lubener]

Listening to an audio clip to diagnose is a waste of time. You have to crawl under and examine the joints or bearing. Usually when they go bad, powdered rust will be present on the joints or bearing. In extreme situations, play and vibrations will be noticed.

 

[JHZR2]

Assuming your MB has flex disks, have the flex disks been replaced?

I replaced flex disks and the center driveshaft support bearing on a w220 some years ago, in my driveway under jackstands to solve a like noise.

Flex discs are original but fine.

Center bearing to me is the culprit.

Listening to an audio clip to diagnose is a waste of time. You have to crawl under and examine the joints or bearing. Usually when they go bad, powdered rust will be present on the joints or bearing. In extreme situations, play and vibrations will be noticed.

When forums discuss about these kinds of issues online there is always a comment about what the noise sounds like. To me the noise is very obvious in the video as are the changes in sound. Not better than eyes on something, sure.

The driveshaft is beneath some sheetmetal noise/heat/dirt protection, and beneath the exhaust. I’m beneath about a foot of remnant snow that hasn’t gotten warm enough to melt. Actually hard enough ice on top of it that it’s a lot to chop and move even to be able to get into a spot where I could get it up and explore. Not to mention ruin everything caked in salt.

So even when I rolled under in my driveway yesterday, there wasn’t anything to see… without a lot of deconstruction….

I’ll definitely look for the powdered rust. IME on MBs, the carrier that holds the bearing, which is a metal ring with rubber bonded inside as a bushing, tends to lose that bond.

 

[RooflessVW]

Flex discs are original but fine.

Center bearing to me is the culprit.



When forums discuss about these kinds of issues online there is always a comment about what the noise sounds like. To me the noise is very obvious in the video as are the changes in sound. Not better than eyes on something, sure.

The driveshaft is beneath some sheetmetal noise/heat/dirt protection, and beneath the exhaust. I’m beneath about a foot of remnant snow that hasn’t gotten warm enough to melt. Actually hard enough ice on top of it that it’s a lot to chop and move even to be able to get into a spot where I could get it up and explore. Not to mention ruin everything caked in salt.

So even when I rolled under in my driveway yesterday, there wasn’t anything to see… without a lot of deconstruction….

I’ll definitely look for the powdered rust. IME on MBs, the carrier that holds the bearing, which is a metal ring with rubber bonded inside as a bushing, tends to lose that bond.

When the rubber goes bad you get a knocking or thumping against the tunnel. When the bearing goes you get a grinding noise.

 

[Lubener]

When the rubber goes bad you get a knocking or thumping against the tunnel. When the bearing goes you get a grinding noise.

You will also get a vibration as everything will shift off center.

 

[nascarnation]

After doing this job twice in 6 months on my Saturn Vue, don't scrimp on the part. The replacement Chinese one I got lasted months before the rubber came apart. Hopefully there's a quality replacement available to you. These days it's often difficult to identify what a quality replacement is. Good luck.

 

[JHZR2]

When the rubber goes bad you get a knocking or thumping against the tunnel. When the bearing goes you get a grinding noise.

Definitely a grinding type noise. Sounds like a seized brake. But all brakes are perfect, and no abnormal heat.

You will also get a vibration as everything will shift off center.

No vibration whatsoever. Extremely smooth across all speed ranges.

 

[JHZR2]

I parked the car because it’s just an extra. Trying to line up lift time, so I was driving around a bit today as I took the day off. The noise went from a dragging brake sound to a high pitch squeal sound, then mysteriously went away.

I almost wonder if the bearing is failing and the 0F weather caused the grease to not flow. Now that’s it’s 42F it moves again. Something like that.

Unfortunately, this is a design where Mercedes doesn’t sell just the center support bearing, even though they sell it for every other car that I own. It’s so stupid to have to replace the driveshaft. Either a $1700 one or the $300 Chinese one. There are a lot of good used ones out there, and there are aftermarket center support bearings, that I might try to get a hold of, and swap a quality bearing into.

But it’s really odd that the sound just went away completely. I didn’t hit anything, I don’t think anything kicked up, and even if he did the driveshaft as well hidden. So I don’t know what would be rubbing, I did get under the car in frigid weather to look.