Noisy 722.9 7g gearbox bearings ??

my 08 ML-420 has recently developed a whining sound, which is particularly noticeable at low speed.

It sounds like the noise is coming from the gearbox area, the vehicle has 123k on the clock now and I have owned it for the last 95k of that. Gearbox oil changes have been done every 35-40k and the valve body was changed at about 40k. Are there known issues with the 7g box bearings ??

I have been in communication with one of refurb places and they say that it sounds like a failed/failing bearing but couldn’t confirm until they get the box (600 miles away). If it was bearings they say that it is a full rebuild @ £3K inc VAT (excluding removal & refitting) and it will take at least a week as they don’t have a similar box to do an exchange.

I guess the alternative would be to look for a replacement box from a breakers, assuming I find one from W164 420CDI is it a straight swop or would I also need my local garage to swap over the valve body/conductor plate?

The noise isn’t too bad at the mo, what’s the worst that could happen if I continued using it as is ?

Mark

 

Can't help with the technical side but I would really want one the top Merc Indys to advise/diagnose this before shelling out any money .

 

Is there any noise at higher speeds? Does the noise rise and fall with engine speed or just rise with vehicle speed?
What tyres have you got on and how worn are they?

 

Tyres are brand new RS3’s, it was there before I changed tyres (previous were also RS3). The noise is still there at higher speeds but less noticeable. It seems to track engine speed, it is more noticeable going up and down the first 3 gears.

Since it started I have changed gearbox fluids and also did the transfer box at the same time. No change.

 

What about rear diff and front diff oils they could have a speed related whine ?

 

Both changed about 6 months ago.

 

You say it tracks engine speed, is it still there in neutral?

 

Also if you have your foot on the brake and increase revs doesn't do it (warning - make sure you have plenty of room in front as if your fort slips off the brake it'll take off like a scalded cat)?

 

No noise in neutral, I will check holding it on the brake tomorrow when I get home.

 

No need. If it did it in N but not held in drive I'd suspect the gearbox input bearing but it's further into the box than that.

 

is it 4 x 4 ?

USA guys all got a free new gearbox because an irreplaceable bearing in the transfer box was made of cheese
lots on USA forums. in Europe we just get a 7k bill


this is the wrong one.... but there is a similar one for the 4 matic

As alleged, Defendant Mercedes-Benz USA, LLC (“MBUSA” or “Defendant”) has known about this defect for years, circulating internal Technical Service Bulletins to its factory-authorized dealerships that detail the nature of the transmission problem. Indeed, the defective 722.9 transmission has failed to such a widespread extent that, at one point, MBUSA was unable to supply sufficient replacement transmission components to have the defective transmissions repaired and, as a result, for a long time, MBUSA prevented independent service stations from purchasing such replacement parts. Worse yet, when the transmission valve body or conductor plate fails in the Mercedes-Benz 722.9 transmission, a real safety hazard ensues. As a result of the defect, the transmission will have a difficult time shifting from first to second gear, and will not shift to higher gears, causing the vehicle to be unable to be driven at any speed. The fault will then cause the transmission to enter what is referred to as “Limp Mode,” leaving the car to “limp” along the roadway in a very restricted and limited fashion. Despite this and despite the clear defect and Defendant’s knowledge of it, MBUSA has failed to take any action. Because the defective transmission typically manifests itself outside the 4 year/50,000 mile durations limit of MBUSA’s New Vehicle Limited Warranty, MBUSA washes its hands of any liability, fails to disclose this defect, and leave consumers of the affected vehicles, like Plaintiffs, to pay for the costly repair of the transmission to the tune of several thousands of dollars.

Plaintiffs, who own a 2007 Mercedes-Benz S-550 originally equipped with the defective 722.9 transmission suffered this fate, had their vehicle’s transmission fail repeatedly on the roadway when the car had just 57,000 miles or so, and were denied any consideration by MBUSA. Given MBUSA’s failure to stand behind its product, Plaintiffs were forced to and did pay over $2,000 to have the transmission valve body replaced. Needless to say, transmissions in cars having only 57,000 miles should not fail—much less should they fail by the thousands in Mercedes-Benz cars across the country. Plaintiffs file this lawsuit to seek redress for MBUSA’s violations of the California Consumer Legal Remedies Act (“CLRA”) and California’s Unfair Competition Law (“UCL”).

 

A transfer box bearing noise will be road speed dependent not engine speed dependent.

 

Many thanks guys. Yes the Ml is 4x4.



I have found a local gearbox specialist who will have a look for me once they have moved premises- about 2-3 weeks.

 

These suffer with transfer box and front diff bearing problems.

 

Many thanks Steve. I will see if my local garage can narrow down where the noise is coming from.

 

If they can't. Drive over to Steve

 

Best of luck!

Usually if its transfer box it whines all the time, regardless of speed. If its a front diff its usually on overrun from 40-50mph downwards, a bit like a wheel bearing noise.

Although I had one the other week that had both....

 

Just a tad to far to travel from North Aberdeenshire.

 

Yep I'll give you that

 

Just got it back from the garage, it looks as if it was the water pump and idler that were making the noise.

I have only driven it for a mile from the garage to the house, but it does sound much better.

Not a cheap job but much better than the alternative.

Mark