So I got this noise on deceleration that occurred soon after getting the A4 going (bought without hearing it run-needing battery). This is my first turbo car...thought might be related to turbo but after driving and checking out conditions that make the sound change it doesn't make sense to me.

The noise is loudest when letting off the gas at speed. You can hear it when the cruise control slows the car but is faint. Getting worse. The sound goes away when you accelerate. The sound continues when decelerating and I put it in Neutral (at speed). The sound is speed related and does not change when in neutral and I rev the engine while decelerating.

Transmission shifts and works fine. Differential? Quattro?

youtube link:
2003 A4 1.8t tiptronic Quattro 157k

 

Anyone have an idea? pinion bearing?

 

You might check the oil levels in the differentials and the transfer (Quattro) section of the transmission. After all these years, they may be a little low.

 

It was a rock between the heat shield and the floor just above the rear Quattro area of the tranny! I do have to replace the rear propshaft seal as it is dripping there...hence thinking it might be the tranny itself making the noise.

Thank you everyone!

 

Mine is leaking in the same place. I've replaced the seal a while back when I did a fluid change. It's leaking again.... I'm going to replace the front drive shaft seals as they are starting to leak too.... The rears appear to be fine. I guess the heat from the engine and exhaust are accelerating the issues. Plus it's got 235K miles on it. I'm not complaining though. It's been a good one so far.

 

How long did a new seal last?

 

Not long for some reason. Next time, I'm going to polish the flange surface a bit before reinstalling it.

 

Did you notice play in the shaft? Wonder if one can replace the bearing closest to the seal...

 

I didn't notice any play but that bearing (a CV joint) can be replaced.