J0nas

Hi, need some advice.
My GL is marking bearing noise from the rear end at 40 km/h. Its increasing and at 55km/h i can hear whining sound. At 60km/h it disapears and comes again from around 80-100 but with much lower noise.
Noise appears only when accelerating. If i release the pedal sound stops immediatelly. All the oils in transmission are changed. Any suggestions?
Mulleage 150k km.
https://youtu.be/1EcDJA4agDw

chassis

Something is not right in the driveline: propshaft, differential or halfshafts.

Whining means high speed, which means either differential or propshaft.

Is there any vibration noted? If you swerve relatively aggressively at highway speed (carefully with no one around you), does the noise change on one side or the other?

Could be bearings or gears in the differential.

J0nas

Hi,

thanks for reply. I have some very slight vibration sometimes on ~100-120 km/h. i thought it's wheels disbalance, but i can feel this slight vibration only some times. so wheels shouldnt be the case.
If I swerve - there is no change in that noise. on the highway this sound is really hart to notice so actually no chance to check if it's changing between the sides.
Bearings of gears shouldn't be as the same noise is while driving on any gear. main indicatior is speed.
Main problem is that it's very hard to diagnose such thing, but it's really annoyng and i dont know how much I can trust this car on long road trips.

chassis

I would focus on propshaft and rear differential.


Tip in/tip out noise as you indicate means torque related. No side to side noise as you indicated means not the wheel bearings or halfshafts.

arsupisemnet

Wheel bearing noise do not disappear with the speed. Faster you go, louder it become.

chassis

You said there is a vibration. This is likely propshaft related. Differential bearing and gear noise is high frequency audible, not a vibration.

It could be propshaft flex coupling, center bearing or u-joint.

J0nas

Just got the diagnose from one of the repair centers. It's the transfer case making sound. They checked this one on the hydraulic car lift. There is DYNO mode on Mercedes, which allows to check such cases.
My question would be if anyone could help with precise part number of the transfer case for the X166 190kW GL350 without off road package.

x166gls

Did you ever get this fixed or find out what the part/problem was? My 2017 GLS 450 is doing the same thing. Slight/Soft grinding sound, only under acceleration at lower RPMs - doesn't matter which gear.

It's not the turbo wastegate loose as when the car is not in gear, revving the engine does not produce the same sound.

Driving me crazy!

x166gls

Took it to the dealership as this was under extended warranty from when I bought CPO. It was the transfer case and it will be replaced under the warranty. Don't know the exact specifics but will post an update once I hear back from dealership.

olesouthernboy

I had to do both the transfer case chain & rear wheel bearings. Both were pretty easy jobs. Transfer case chain & most all bearings can be done without removing the case. I just changed the chain about 100k miles ago, no bearings. Cobra transmission in FL has a complete rebuild kit for it.

x166gls

Dealership replaced transfer case and small sound continued. Ended up being drive shaft (propeller shaft). They replaced this too and the sound has now gone away.