I will be shocked if anyone has experienced this same problem. My PTT does the strangest F!@#$%@g thing when it gets wet underneath. It starts making this noise, like something is vibrating and bouncing around between the front wheels and driver and passenger seats. It ONLY happens when it gets pretty wet, BUT it is not consistent. Meaning, sometimes when idling it would be faint, while driving it comes out of being very loud to then eventually going away after driving at a consistent speed.
When it does this, it sounds like the exhaust is muffled.

I know this all sounds bizarre, but it is the strangest thing,,,

 

Throw it on life and check stabilizer bar and bushings

 

Thank you! I will check it out, it does sound just like them, but when I replaced on my 9964s it made the noise consistently wet/dry

 

And NOISE****

 

Any noise when going over bumps or dips in the road? More noticeable when cold out?

 

That was what made it so obvious on my , it hasn't made any noise yet (aside from a little bit of crunching). It is definitely worth checking out

 

Broken cat maybe?

 

My theory may be bizarre as well: moisture affecting the crank/under-drive pulley and/or belt. Water may be somehow causing noise while the pulley is spinning (your idle noise). Going from loud to quiet may be centrifugal force due to engine speed increasing may be drying the pulley as your drive.

So, maybe it's a pulley and/or worn drive belt issue?

 

I just had the car in for a recall and they did mention the belt needing to be replaced soon, while your theory is a little bizzare it does make the most sense as it is only when heavily wet not just a sprinkle... definitely work investigating Thank you!

 

I know - totally bizarre but that's the only thing I could think of involving water. Hope it all works out.

 

Here is another idea thrown out there, have you checked your radiator fans? What if part of one blade is cracked, or something is stuck there? Check the fans.