My trusty 2007 GL450 just tuned 100k on it. About two months ago I started noticing a bit of a humming noise coming from somewhere either in the middle of the car of from the rear end when driving about 35 miles an hour. The set of tires that I had on the car at the time was getting pretty low on thread so I figured that the noise was coming from rear tires that were coming close to wear bars.

Got a brand new set of tires last earlier this week but the noise is still there. Not sure what to do next to troubleshoot. The noise is not whinny like you'd hear with various pulleys or transmission pump. It's rather humming and becomes pronounces at about 40mph. As I said, it feels like it's coming either from the back of the car or from the middle.

Here is a video I shot this morning. Hope some may have ideas.

I watched couple minutes. Once it is making the noise- if you let off the throttle does it make it? Does it make it if you throw the truck in neutral and coast at that speed?

Does it do it when you turn slightly? What about if you turn more decisively?

Does it do it in different gear/ rpms or is it strictly speed related?

Do the above and let us know. Low frequency sound is hard to pinpoint- it could be coming from anywhere. You have to divide and conquer. It is either from drivetrain (engine/tranny/driveshafts/ diffs) or from bearings

Let us know.

The noise is present once you get up to 35-40mph. If you let off the throttle (release the gas pedal) it is still there. I also got up to 60mph and put truck in neutral -- the noise was still there.

There is no difference in noise if I turn the wheel slightly or do it more decisively.

The noise seems to be speed related and not gear specific.

Wheel bearing or driveshaft u-joints or rubber cakes would be my initial guesses.

Also while at it try full lock slow turn each way and see if there is some clicking / thumping upfront. You are right at the mileage when the pass side cv joint goes bad.

Hi Alx,

Definitely heard some clicking noise up front coming from CV joint. Do you recommend changing just the passenger side or both at the same time?

Thank you for your feedback.

Alx, is there any good way to test/diagnose any of the parts above? Or just start changing them one by one hoping that the noise would go away?

Check your exhaust manifold, read this thread:

https://mbworld.org/forums/gl-class-...d-humming.html

More similar discussions:

https://mbworld.org/forums/gl-class-...ow-speeds.html

Hope this helps.

From your video, I noticed you're on Pomerado Rd. (Poway) & Scripps Poway Parkway (Scripps Ranch). We're probably neighbors!

sort of.

a bad wheel bearing will develop eventually play and roughness when spun slowly

a bad cv joint usually tears the rubber boot and dirt inside makes it fail. they also get progressively more noisy in a short period of time. you can try also full lock slow driving with some throttle application preferably up hill to try to hear it clunk/click/etc. you dont need to replace them in pairs. for some reason the driver's side joint is never the issue- the pass side being longer usually fails.

the rubber cakes on the driveshaft can be inspected visually for cracks and tears

u-joint can be pried with a metal bar and checked for play

but if you hear the cv joint make noise when turning... it is most likely the culprit or it needs to be replaced anyway

Yes, I am closer to the VONS center right off Scripps Poway Pkwy. Where are you?

Took the car to my indy mechanic. Three different mechanics drove the darn thing and everyone could definitely hear the noise. Rear wheel bearings were the prime suspects but since it would be a costly 5+ hour job to replace each side, I decided not to risk it and took it to the dealer for a second opinion.

Dealer came back with the verdict that it was in fact left rear wheel bearing. They also found a bunch of other things on the car that needed IMMEDIATE attention and would only cost $2000 to fix . I told them to hold off until we can address the main concern. Dealer quoted $800+ to replace wheel bearing with $600+ being in labor cost.

Ordered wheel bearing today and waiting for it to arrive tomorrow.

LOL. I'm three blocks east from there, near EBS and St. Gregory The Great Church.

Hope things work out with your GL!

keep us up to date on whether this solves your problem

Picked up the truck from the dealer this afternoon. They changed rear wheel bearing on the driver's side. The noise is completely gone now. Total labor was $605 with a 10% goodwill discount. Bearing cost $98 wholesale. Ouch!

The dealer also found oil leaks at camshaft plugs (all 3) and oil separator/centrifuge cover. They wanted close to $400 for parts and labor to take care of it. Took me about 30 minutes to do it at home. Parts ran about $80 wholesale. I believe the camshaft plugs and centrifuge cover are both prone to leaking oil at about 100k miles. I recommend that you check yours regularly.

I see we have big community of GL drivers in San Diego from mbforum=) Noise from video also reminded me of wheel bearing. My first thought was cheap tires, I had cheap tires on my E500 and this humming noise was driving me crazy, checked all bearing and nothing, noise went of after switching to Michelin.

Also if you need very honest and MB specific mechanic take your car to 9585 Black Mountain Rd, "Silver Arrow" It is owner operated, and those guys are amazing in their MB knowledge and fair prices. And most important they wont screw you to pay to fix something if there is no necessity to do so.

I guess there are quite a few GL owners down here in San Diego. I certainly see many GLs driven around town. It would be fun to organize a meet up over coffee for GL fans of San Diego.

Thank you for mentioning Silver Arrow -- I have definitely seen their shop as my daughter's dance studio used to be right off Black Mountain Road near where Silver Arrow is located. I will definitely keep them in mind.

The indy shop that I have been going to for the last 8 years is called Exclusive Motors located off Miramar Rd at 8448 Miracrest Pl. Michele (the owner), Vince and Bob are all certified MB mechanics. They only work on MB cars so there is definitely a wealth of knowledge you will find with these guys. They are also about 30% less expensive than a typical MB dealer when it comes to labor rates. And they don't perform any work unless it's really needed for your car. Highly recommend Exclusive Motors to any MB owner in San Diego.

Speaking of E500 -- I used to own 2003 model and loved the car. It used to 'eat' tires so I needed a new set every 20k miles (I ran a staggered set up).

I recently came across an opportunity to buy 2003 E55 with only 30k miles on it in immaculate condition. The color was the same as my old E500 (pewter). Almost wrote a check for it but manage to contain myself as I don't need another project in life right now.

With respect to GL -- bad wheel bearing indeed sounded like bad tires. This was my initial thought the first time I noticed the noise. But once the tires were changed and then noise was still there, I new it had to be something else.

Cheers!
Alex

Small world. I frequent Sport Utility Motorcars (8448 Miracrest Pl # E, San Diego, CA 92121) for my European repair needs (BMW, Land Rover) but not with my GL, yet(still under warranty). Behr, the owner saved me tons of money on costly "inspection" repairs and his labor rates are also much less than the stealerships. He's always busy with Land Rovers, BMW, Porsche, Mercedes in his garage.

Glad to hear your GL is back in shape!