[Tonyvandijk]

I own a GLA 250 4-Matic and have now approx. 3000 miles on it.
When driving between 1000 and 1200 RPM, I experience a grumbling sound. It's just like the engine does not shift back in time or if the exhaust pipe is a bit loose and vibrates. When the sound appears and I shift back with the manual control, the sound disappears momentarily. Does anyone have a similar experience?

 

[Boris_Balkan]

It's the transmission still in a REALLY high gear with revs very very LOW while you are going slow. The TCU has not chosen the 'best' gear to be in, rather it has chosen the 'most-efficient.'

Common noise/vibration in fuel-efficient 4-cylinder cars.

To test it, put the GLA in manual mode. Coast along at about 20-25mph, but put it all the way into 6th or 7th and push on the gas, it should re-create that sound

 

[Tonyvandijk]

Thanks. I believe you're right, but can anything be done about it because it's very annoying?It happens in speeds between 30 and 50 mph while transmission between 5 and 7. These speeds are very common in city traffic, so the noise happens quite regularly.

 

[Boris_Balkan]

Use manual mode or put her in 'sport' mode after warm-up.

 

[Tonyvandijk]

I tried, it doesn't really help. Nobody else has this problem?

 

[Boris_Balkan]

Take a video, I'm very curious.

Is this your first turbo-4-cylinder? There are many familiar sounds for those attuned to this driving experience, so we might miss exactly what you're describing.