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Discussion Starter · #1 ·
Has anyone noticed a single click or knock type sound in the front end when creeping at low speed around parking lots or pulling into garages? I hear it when a window is open and I've just taken my foot off the gas either in drive or reverse, but doesn't occur in neutral. Can't hear it when the window is up. Driving slowly by a wall or into a garage amplifies the sound due to reflection. My dealer service rep heard it when I brought it in and after he checked with a Subaru master tech who happened to be there that day I was told by the master tech that it's a normal sound created by a servo (I believe he said related to the CVT transmission). He said they all make that sound and sure enough, after my asking to hear another Ascent on the lot, that one produced the same sound. Just curious if anyone else has heard it too and whether the CVT servo answer I was given sounds correct.
 

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The CVT has servos that drive the hydraulics that are a part of the torque converter lock, as well the ones related to spooling up the pulleys that drive the chain.

I've never paid attention to mine, but perhaps they make such sounds? The sound I usually hear happens when I shift into a gear, and it sounds like air escaping from an old school water kettle for a fraction of a second when you shift into gear.

It's quite plausible that the system would make a pop type sound instead.
 

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Discussion Starter · #3 ·
The CVT has servos that drive the hydraulics that are a part of the torque converter lock, as well the ones related to spooling up the pulleys that drive the chain.

I've never paid attention to mine, but perhaps they make such sounds? The sound I usually hear happens when I shift into a gear, and it sounds like air escaping from an old school water kettle for a fraction of a second when you shift into gear.

It's quite plausible that the system would make a pop type sound instead.
While I was at a different local dealership yesterday getting the just released Starlink Rel 4.18.25.50 software update, I asked the service rep about the single knock/pop sound just to get more input. After he and the transmission tech heard the knock and we heard the same produced on another Ascent on the lot, they felt it was caused by the turbo wastegate opening after lifting foot off the gas pedal. The method used to demonstrate the sound was left foot on the brake pedal, car at a standstill, in drive or reverse, and right foot feathering the gas pedal. They both felt it was a turbo wastegate opening sound as opposed to being associated with the CVT. My thought was the wastegate opening would produce sound like an “old school water kettle “ as you perfectly describe. I’m just trying to identify where the sound is coming from. If anyone has any further thoughts I’d appreciate hearing more.
 
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