Hissing sound from passenger side vent?
 

I have a hissing or breathy sound coming from the passenger side...maybe the area around the vent. Doesn't seem to be effected by rpms. Any ideas what this could be or where to start looking? It's an 82 300td

Have you got central locking that doesn't work?

Or are you getting confused with wind noise from a nadgered door seal?

My bet would be on a leaking vacuum pod... the rubber gets old and starts cracking.

Not a door seal and no auto locks. Where in that area are there vacuum lines? Or "pods"?

Well the only thing towards that side of a car in the cabin (LHD I hope!) could be air conditioning stuff but that's normally towards the centre of the car rather than right out by the door.

Other than that out side of the car vacuum lines for an automatic transmission - but could also just be wind noise from a hole in the front bulkhead under the battery tray...

...oh and it isn't something daft like an open passenger side vent that's normally closed is it?

The fact that the noise seems to be consistent no matter what speed I'm going at makes me think a vacuum line would make sense. Also the shifting has been rougher than usual lately. The trans vacuum lines are down below the car though correct? Not anywhere near
The battery?

Remove the kick panel on the passenger side, start the car and listen for the sound, you should be able to find it.

This may take away enough vacuum to affect the transmission.