I have a 2018 C300 with the 9 speed automatic gearbox. It has about 20000 miles on it and I've only owned it for just over 2 months. Over the past week I've noticed when in sport mode I can hear a squeak when changing gear, more so down shifting. I couldn't hear it at all in comfort mode but going back to sport mode again it appears instantly. It is only during the gear change and almost sounds like a squeaky bushing. Any ideas?