So I added the cab to box bottom seal to my Limited in hopes it would make the whistle go away. However, it seems to have made it worse.
When recirc is off it whistles above 45mph. When recirc is on it whistles below 45mph. Very easy to replicate, does it every time I drive it.
I took it to the dealer for the power steering recall and told them in detail about this annoying whistle.
The tech who test drove the truck said it was the roof rain gutter moldings. I told the service rep that I know it isn't that because I have taped everything on the outside with painters tape and none made any difference. I told them it is something related to airflow through the cab and their response is, well that's strange, we'll replace the roof moldings anyway.
Everyone who rides in the truck says, what's that whistle, my reply, I'm driving a very expensive tea kettle.
RAM really needs to figure this out.