FreeWoRLD

I have a 2018 GLC 300 4matic and recently started hearing about this tapping noise. I was wondering if anyone has any suggestions on what the cause could be.

Some findings;

• Happens only when in gears. Nothing when stationary, even in high rpm
• More noticeable when driving back from work afternoon (on my way home from work). Worse when engine is warm? In mornings, either don’t hear it or it is really low, i can’t tell
• After 5th gear or so with higher speeds, I don’t hear it anymore. I would say noise is the most between 20-50 mph, not sure though
• As I drive for longer periods (20+ mins), the less the noise gets, but it is there, even at minimum
• Tried putting in neutral when cruising and the noise immediately goes away. Revving the engine when cruising on neutral does not produce this tapping noise at all. Absolutely no noise coming by revving the engine in neutral. It is very quiet and smooth
• Pretty much the noise follows the rpm. When transmission upshift, the noise stops between the shifting action and resumes with the new gear on
• When I let go of acceleration, the noise goes away
• Oil is at right level and I don’t have any codes when scanning
• Just for information; I had a transmission fluid change at official dealership back in July - around 7,000 miles ago. Not sure if I always had the noise and no idea when it started

I can’t come up with anything. Any suggestions?

DanD.

I would put the car on stands so wheels can spins, turn on the engine and start "driving" and listen where is the sound coming from.

FreeWoRLD

Good idea, I will try to do that. Thanks

mikapen

Ask your dealer to mount some Chassis Ears to target the noise.

W205C43PFL

Got this figured out at all OP? Curious.

FreeWoRLD

Not yet but I have an appointment in 2 weeks. I’ll share the outcome

W205C43PFL

Sounds good.

FreeWoRLD

They said they can’t replicate it. I’ll have to take it to Mercedes-benz dealer at another time.

W205C43PFL

Sorry to hear that, did they use chassis ears?

FreeWoRLD

They definitely did not, but this was Carmax that I should have mentioned.

I have an extended warranty with them until 125,000 miles and I just wanted to bring the car to them in the first place.

Maxcare (Carmax extended warranty) covers MB delaerships as well, so that will be my next stop, whenever I get a chance.

W205C43PFL

I see, hopefully that works out.

Mossie

Check the Prop Shaft coupling, it seems it’s time to replace it.

W205C43PFL

This might indeed be it OP, hopefully this solves it.

alora2

A tapping noise that occurs only when your vehicle is in gear could indicate a few potential issues with the transmission, engine, or drivetrain. Here are some common causes to consider:

1. Low Transmission Fluid: Low transmission fluid levels can cause irregularities in the operation of the transmission, leading to tapping or ticking noises. Check your transmission fluid level and top it up if it's low. If the fluid is significantly low, there might be a leak that needs to be addressed.
   
2. Worn Transmission Components: Tapping noises in the transmission can also be caused by worn or damaged components such as gears, bearings, or synchronizers. If the transmission is old or has not been properly maintained, these parts may wear out over time and produce noise when the vehicle is in gear.
   
3. Faulty Torque Converter: A malfunctioning torque converter can also produce tapping or ticking noises when the vehicle is in gear. Issues with the torque converter's internal components, such as worn bearings or damaged fins, can cause noise during operation.
   
4. Engine Issues: Sometimes, tapping noises that occur only when the vehicle is in gear can be related to engine problems. This could include issues with the valvetrain, such as worn lifters, valves, or camshaft components. Low oil pressure or insufficient lubrication can also contribute to engine noise. FMWhatsApp
   
5. Driveshaft or Axle Problems: Tapping noises in the drivetrain, particularly when the vehicle is in gear, could indicate issues with the driveshaft, CV joints, or axle shafts. Worn or damaged components in the drivetrain can produce noise as they rotate under load.
   
6. Exhaust System Issues: Problems with the exhaust system, such as loose or damaged components, can sometimes cause tapping or rattling noises that are more noticeable when the vehicle is in gear and under load.
   

If you're experiencing tapping noises while your vehicle is in gear, it's essential to have it inspected by a qualified mechanic as soon as possible. Ignoring such noises could lead to further damage and potentially more costly repairs down the line. A professional inspection can help diagnose the root cause of the issue and determine the appropriate course of action to resolve it.

FreeWoRLD

Thanks for your suggestion. I am curious if the prop shaft coupling stops turning the second you are in neutral (out of any gears)? I am asking this because the noise goes away immediately when I put it in neutral (when cruising). It also stops momentarily between shift changes. By the way, now the weather is warmer I don't even notice it and if I do, it is really low.

I haven't had a chance to take it to anywhere yet, but I will at some point, and I will make sure to update my post here.