vic300

Just wondering if anyone else's C300 makes the same noise as mine. When decelerating in gear from a high RPM to a lower RPM the car makes a loud noise between 3000 to 2000 RPM. Sounds like a propeller plane almost, its a really annoying whine. Only happens when I'm off the gas and slowing down. For example, if I'm coming to a stop and use the paddles to downshift and engine brake I'll hear the noise. Same thing if I'm doing some sporty backwoods driving and slowing down for curves. Can't really hear it in Comfort mode since the RPMs don't get that high but its really prominent in Sport+ and Full Manual. Also, it kind of sounds like its coming from the rear so it might be the diff, but could very well be the tranny . What your thoughts/experience regarding the the tranny/diff?

Jinzen

Yup normal. On my car and the loaners.

Glyn M Ruck

If it's diff noise it's very easy to check with everything off in the car ~ sound etc. Play the throttle gently from on to trailing throttle & the noise will come & go. Sign of pinion bearing having lost preload.

What you describe however sounds like the turbo controller dumping uneeded boost.

vic300

Hmmm makes sense if it's the turbo controller. I wouldn't expect Jinzen and his loaner to be defective then too. This is my first turbo car so still getting used to the engine. That must be a lot of excess boost though cuz the noise is pretty significant.