Knocking from rear passenger side?
Thread Starter
Rennlist Member
Joined: Jun 2016
Posts: 165
Likes: 2
From: Indianapolis, IN
Knocking from rear passenger side?
I've tried to find someone with a similar problem on Rennlist so bear with me if this covered somewhere.
I have a relatively new to me 2014 Cayenne Turbo S with about 90k miles purchased in July 2025. I did a Fabspeed secondary cat delete when I bought it.
Recently had the air compressor and manifold replaced, followed by the front and rear air shocks replaced. This was done piecemeal to try to address an issue with the air suspension, and since all parts were replaced, the air suspension works well. However, after the compressor was replaced, when I went to pick up the car from the mechanics, I heard a fairly loud knocking coming from the rear passenger side (as best I can tell) when first pulling away that then resolved and didn't return until the next morning. I only hear this noise when the engine is under load (so the car is moving) and not when I rev the engine when sitting idle. I also have not heard it when revving the engine in neutral when the car is moving. It tends to come up around 1500-2000 rpm, and it definitely goes away in a few minutes. When I hear this noise, I don't notice the car driving any differently, I don't notice the "crunching/grinding" noise people have described when the transfer case is shot.
I had the mechanic drive with me yesterday and they did hear the sound. They then put the car on the lift and could not replicate the sound when revving the engine because it only happens when the car is moving. They (and I) checked under the car and did not see anything loose or knocking.
They mentioned it could be the exhaust itself (as in interior baffles), which I would be happy to replace with a Fabspeed Maxflow exhaust if I knew it would fix the noise.
So, any ideas of what this could be? Initially thought it was something to do with the suspension work or something that was disconnected, but neither the mechanic nor I can find anything that would be related. Or any ideas of how to confirm it is coming from the exhaust or elsewhere?
TIA
Brian
I have a relatively new to me 2014 Cayenne Turbo S with about 90k miles purchased in July 2025. I did a Fabspeed secondary cat delete when I bought it.
Recently had the air compressor and manifold replaced, followed by the front and rear air shocks replaced. This was done piecemeal to try to address an issue with the air suspension, and since all parts were replaced, the air suspension works well. However, after the compressor was replaced, when I went to pick up the car from the mechanics, I heard a fairly loud knocking coming from the rear passenger side (as best I can tell) when first pulling away that then resolved and didn't return until the next morning. I only hear this noise when the engine is under load (so the car is moving) and not when I rev the engine when sitting idle. I also have not heard it when revving the engine in neutral when the car is moving. It tends to come up around 1500-2000 rpm, and it definitely goes away in a few minutes. When I hear this noise, I don't notice the car driving any differently, I don't notice the "crunching/grinding" noise people have described when the transfer case is shot.
I had the mechanic drive with me yesterday and they did hear the sound. They then put the car on the lift and could not replicate the sound when revving the engine because it only happens when the car is moving. They (and I) checked under the car and did not see anything loose or knocking.
They mentioned it could be the exhaust itself (as in interior baffles), which I would be happy to replace with a Fabspeed Maxflow exhaust if I knew it would fix the noise.
So, any ideas of what this could be? Initially thought it was something to do with the suspension work or something that was disconnected, but neither the mechanic nor I can find anything that would be related. Or any ideas of how to confirm it is coming from the exhaust or elsewhere?
TIA
Brian
Rennlist Member
Joined: Jun 2018
Posts: 51
Likes: 37
From: Sugar Land, TX
The first thing I would check (because its easy) is the driveshaft center support bearing. Car 12 years old, 90k, plentiful torque. Prove thats not the problem first.
If its failing the noise couid sound like its coming from that area. Only moving and under load would sound about right. Mine went away after about 10 minutes driving but I wasnt satisfied it was nothing. Glad I persisted.
If its failing the noise couid sound like its coming from that area. Only moving and under load would sound about right. Mine went away after about 10 minutes driving but I wasnt satisfied it was nothing. Glad I persisted.
Thread Starter
Rennlist Member
Joined: Jun 2016
Posts: 165
Likes: 2
From: Indianapolis, IN
The first thing I would check (because its easy) is the driveshaft center support bearing. Car 12 years old, 90k, plentiful torque. Prove thats not the problem first.
If its failing the noise couid sound like its coming from that area. Only moving and under load would sound about right. Mine went away after about 10 minutes driving but I wasnt satisfied it was nothing. Glad I persisted.
If its failing the noise couid sound like its coming from that area. Only moving and under load would sound about right. Mine went away after about 10 minutes driving but I wasnt satisfied it was nothing. Glad I persisted.
Thread Starter
Rennlist Member
Joined: Jun 2016
Posts: 165
Likes: 2
From: Indianapolis, IN
An update: was able to use chassis ears and it definitely sounds like it's coming from the exhaust. My mechanic also was able to induce the knocking sound when it was on a lift and said it's definitely coming from the exhaust. He tried to use a boroscope in the exhaust but wasn't able to see anything broken but next step is replacing the exhaust with a Fabspeed unit and see if that fixes the problem!
