Rear judder noise related to MOE tires or Rear Diff Oil?

Haven’t you asked exactly this before? You even thanked me for my response. 🤷‍♂️

Yes you are correct 👏 but the issue is still there and wondered if it could be related to the run flat tyres.

JamieG74 said:

Yes you are correct 👏 but the issue is still there and wondered if it could be related to the run flat tyres.

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Well, the stiffness of the “MOE” tires certainly doesn’t help, although they’re not as stiff as a “full” run flat. Of course be sure your tire pressure is appropriate for you own climate and vehicle loading.

Personally I get nervous about the health of the rear diff. Changing the oil is a quick and easy maintenance item.

Wayne said:

Personally I get nervous about the health of the rear diff. Changing the oil is a quick and easy maintenance item.

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Looks like we now need a 3rd OP thread entitled "Rear judder noise related to rear diff oil?"

So is this a thing then? I am new to Mercedes and rear diff oil issues so please excuse me.

JamieG74 said:

So is this a thing then? I am new to Mercedes and rear diff oil issues so please excuse me.

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It's not really a thing unique to Mercedes, although the GLA45 AMG version (in @Wayne 's case) as you would expect typically encounters more spirited driving wear than the base GLA250.

I used to pay a lot of attention to the rear diff in my Mazda RX-8/Miata sporting days.

I will certainly be suggesting this to be checked out when I next take car to the local Mercedes specialist.

Just FYI, manufacturer's recommended maintenance intervals are negotiated between engineering and sales departments.

Motor oil change is thus recommended at 10K miles. But if you do UOAs (used oil analysis) you will find that the long chain molecules that control viscosity start to shear and break down by 5K miles. So oil changes really should be done at no more than 5K mile intervals.

There have been reports of rear diff failures. So Forum members may be biased toward more frequent service intervals to avoid future expensive repairs. I change mine every other motor oil change (5K miles on motor oil, 10K changes on rear diff oil).

Call me paranoid, but as the saying goes ... Show me what an over lubricated bearing looks like!!!

That is a good point and I have booked car in on Wednesday for them to investigate. I will report back hopefully with an answer. Thanks for your time.

My 2018 started doing that around 90kmi. Changing the differential fluid instantly solved it. I am at 123kmi and no further issues.

Huey52 said:

Looks like we now need a 3rd OP thread entitled "Rear judder noise related to rear diff oil?"

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Wow! The replacement of the differential at 50K miles is thousands of dollars, no help from Mercedes, yet a common factor for the GLA AWD. one GLA owner has put 3 in, one every 50k-60k miles!

SusanM said:

Wow! The replacement of the differential at 50K miles is thousands of dollars, no help from Mercedes, yet a common factor for the GLA AWD. one GLA owner has put 3 in, one every 50k-60k miles!

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I must say, you never pass up an opportunity. 😆
I guess we don't need a discrete "Rear judder noise related to rear diff oil" as this MOE Tire thread has now migrated to same [and title so augmented]. 🤷‍♂️

JamieG74 said:

That is a good point and I have booked car in on Wednesday for them to investigate. I will report back hopefully with an answer. Thanks for your time.

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And the report back is?

Wayne said:

Just FYI, manufacturer's recommended maintenance intervals are negotiated between engineering and sales departments.

Motor oil change is thus recommended at 10K miles. But if you do UOAs (used oil analysis) you will find that the long chain molecules that control viscosity start to shear and break down by 5K miles. So oil changes really should be done at no more than 5K mile intervals.

There have been reports of rear diff failures. So Forum members may be biased toward more frequent service intervals to avoid future expensive repairs. I change mine every other motor oil change (5K miles on motor oil, 10K changes on rear diff oil).

Call me paranoid, but as the saying goes ... Show me what an over lubricated bearing looks like!!!

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Mine is nearing 10K miles, still in warranty. How much does the dealer charge to replace the rear diff oil? Rear diff oil change isn't mentioned at all under A, B or add-on/interval-based service. Any reason why?
Also, is the rear diff thing relevant to only the 45 or to all models? I will have them do it this year if you deem it necessary because I will be right at 10K miles at the next service.

Edit: is there any specific behaviours that cause the differential to fail? I don't do a lot of "performance" driving or hard cornering or anything, but the roads have tons of potholes and ruts where I live.

I DIY so I can't give a dealer figure.

The 45 recommends a differential oil change at 10K miles and then every 20K miles after that. FWIW, transmission oil change is every 30K miles.

There have been enough failure reports that every 10K miles seems prudent. It's an easy DIY, even if you don't have a lift. Just make sure you can remove the fill plug before you remove the drain plug!!!

RamaGLA said:

Is there any specific behaviours that cause the differential to fail?

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Be reminded why there is a differential. If the oil is becoming laden with contaminants it will start to feel uneven in turns (dare I say a "judder"). However no real adverse behaviors, although of course very hard track-worthy use will more accelerate wear.

Fluids are the lifeblood of vehicles and as @Wayne well cites there's no such thing as an over-lubricated part (however don't overfill oil pan/trans/diff - hard to overfill the diff and most trans).

We here are predominantly automotive enthusiasts and therefore don't solely rely on OEM marketing-engineering compromise schedules, but rather augment with our own reason and experience applied to our specific use cases.

Wayne said:

Just make sure you can remove the fill plug before you remove the drain plug!!!

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I once almost got lazy and didn't do so; thankfully almost. One can imagine how disastrous to suddenly have an empty diff with no immediate way to rectify!

Huey52 said:

Be reminded why there is a differential. If the oil is becoming laden with contaminants it will start to feel uneven in turns (dare I say a "judder"). However no real adverse behaviors, although of course very hard track-worthy use will more accelerate wear.

Fluids are the lifeblood of vehicles and as @Wayne well cites there's no such thing as an over-lubricated part (however don't overfill oil pan/trans/diff - hard to overfill the diff and most trans).

We here are predominantly automotive enthusiasts and therefore don't solely rely on OEM marketing-engineering compromise schedules, but rather augment with our own reason and experience applied to our specific use cases.

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Thank you both for the insight. I have always been told to follow the manufacturer's maintenance schedule as it is commonly said that "they know best". Since I have never been told to change the oil in the differential, I thought I should check since I'm nearing that 10K miles point.

RamaGLA said:

Thank you both for the insight. I have always been told to follow the manufacturer's maintenance schedule as it is commonly said that "they know best". Since I have never been told to change the oil in the differential, I thought I should check since I'm nearing that 10K miles point.

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In the absence of any other knowledge and/or experience it is best to follow the OEM schedule, as in general they know best.

However as we've mentioned the Benz schedule is a compromise:

-Engineers, knowing what may befall any mechanical system would have you change the fluids more often.

-Marketeers, wanting to portray their vehicle as very reliable with a relative minimum of maintenance would have you change fluids less often.

So they meet somewhere in the middle, or more likely marketing-leaning. However in fairness the mandated 'A' & 'B' service intervals (especially the 'B') many would deem more often.

Benz can't know how every owner will use their vehicle. You do yours.