Gilley:
Just picked up my new Ml500 SE and was noticing on the way home on the freeway, a humming noise from the rear. It happens on de-acceleration only from about 75 down to 60 MPH. I can change it with the throttle! I had a 00 430 prior to this and heard no such noise. Is it possible that the exaust on the 500 is louder than the 430? The reason I say exaust is that I left it in 3rd gear by accident after coming off the freeway and when I slowed down I heard the same noise, otherwise I might blame the center driveshaft bearing. I would hate to think that was true on a new truck with only 100 miles on it! Any prior experience by anyone?? Thanks!!

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David L

I have the same problem with my 2002 ML320. I took the car to the dealership and they replaced my differential fluid but it did not help. I am trying to fix the problem, but it's hard to do since mercedes technicians sometimes don't know how to fix their cars.

I just took my ML500 in for the 1k check. The shop foreman and I drove it and he agreed there is a slight noise there. They ran it on the rack and determined it is the front differential. By mutual agreement we have decided to run it for a few more thousand miles. If it gets worse they will change it. Being an old gear head I know it will, and they have always taken care of me with both my ML's so Iknow they'll do what they say! I drove 2 other 500's when I was there and they were silent. Maybe Gilly can help us here. Gilly I thought ZF always ran these units in on a test stand before they were shipped to this country, or do they just spot check them. I can't believe they would put out a bad one, but they did this time!

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David L

Brand new and doing 75 mph.... doesn't the owners manual still require a break-in period? Hope you don't get any bearing/cylinder wall scoring...

I had rear differential noise, I called it a slight whine, on a 1983 240D. I bought car with 19K miles on it when it was one year old. It made the noise at 55mph to 60mph, the legal speed limit at the time and hence the speed it would be driven on the interstate.

The rear differential was replaced under warranty and I drove that car for years and sold it with 279K miles on it.

If the speed that your differential makes the noise is a speed that you regularly drive, then you need to get your diff. replaced, the noise will not go away.

First to RoninSC: Yes, I know the noise will not go away. I'm an old GM mechanic and have built several gearsets myself in the 60's. They're either right or they're not, they never heal up. My dealer agreed that it will get changed, but wants some more miles on it so he can justify it. They've always taken care of all my Mercedes and see no reason why they won't this time. T hanks for the input

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David L

To ML320Guy: On page 196 of my owners manual it states for the first 1000 miles not to drive at a steady speed and don't go beyond 2/3 of maximum RPM. Max being 6000, so 2/3 would of course be 4000 rpm. I haven't done that! Final drive ratio on a 2005 Ml500 is 3.70 X .83 overdrive= 3.07 final. With 29.1 tire diameter @ 2700 RPM = 76 MPH. I've done that! @ 4000 rpm your speed would be 112 MPH. I'll probably never do that! I have 1500 miles on it now and the oil level hasn't moved. I drove the 430 I had the same way and it never used any oil up until I sold it with 46K on it. I think with the hard aluminum cylinder walls and low tension rings in the 133 engines you're pretty safe. The biggest danger to going fast in a new vehicle could be the ring and pinion gears. My 500 had 28 miles on it when I picked it up, so I don't know how it was driven before I got it. All I know is I'm happy with it, and in the end my dealer will take care of me. He always has!! Thanks for your input!!

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David L

Made a typo. Meant to say 113 engine! Thanks!

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David L

On my 99 ML320 they changed the center bearing. Solved the problem

This is just one more of those Alabama made Benz issues.

Get a "Made in Germany" one next time. The difference in quality is astonishing.

With all due respect I kind of doubt that. Especially as it relates to the rear differential.

Mr. Bayer. The engines and differentials are made in Germany and shipped to Vance, Al. The transfer cases are made in the US by Borg Warner gear company! Go to any of the Benz forums and on search you'll find German built Benz's that have had gear noise too! Not a big deal to me, as it will be fixed! The big deal to me is somebody who doesn't know what they're talking about!!

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David L

Or read my post #5 above. I’ve had one that made rear differential noise. And that 240D was by far one of the very best MB I’ve owned.

Why some differentials are noisy
The rear differential noise is most probably from the ring and pinion gear. On one of my other vehicles where I disassembled the rear diff to replace friction discs for the LSD I would mention that the workshop manual indicated that the setting of the drive pinion and the ring gear is a determining factor for service life and smooth running of the rear axle drive. It goes on to say that drive pinions and ring gears are checked for good tooth contact pattern and low noise in both directions of rotation on special test equipment and are therefore matched during production. When I reinstalled the diff. I put it back with the ring gear contacting the drive pinon gear in the same position as when I removed it.

I'm sure mercedes does the same thing, but that some get by that should have been set differently or had new ring and pinions.

Ron. I hope Mr. Bayer read it. I'm sure your 240D was built in Germany. Like I said in an earlier thread I was a GM mechanic in the 60's and in my shop I was the only one that did differentials and standard transmissions. Probably the most important setting is the pinion depth. On new gears a number that is etched on the gear tells you the amount to shim it to get proper depth. Then the backlash and bearing pre-load need to be correct too. All this is very critical and it's easy to have a slight noise, so I'm not blaming ZF gear company for the slight noise I have. My local MB shop foreman hears it and when he gets permission from Mercedes he will change it out. I doesn't really bother me, but after you write the big check for one of these you want it right!!

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David L