Strange whistling sound..... more

[gfs1943]

Originally Posted by Randyman1

The whistling sound is a vacuum leak, probably a hose cracked where it attaches to a port. This leak will affect your transmission's shift as it has a vacuum module for shifting. Find the vacuum leak, and the clunking will go away as the leak is causing the hard shifting. Randy

I'm with Randy on this one! if both issues started about the same time they're related.

[BDWEAK]

It may not be a vacuum leak. Most vacuum leaks get louder as you accelerate and disappear as the load on the engine decreases. They normally do not show up a certain speed. I am not rule ling it out, it just seems unlikely with the information given. Will love to here what you finally out the cause. Yes I do know how much Ford loves to use vacuum on their engines.
Not trying to start anything, just my opinion.
Very new to the form, have learned much reading the threads, so thanks.

[SafetyFirst]

We have a 2007 Holiday Rambler Neptune diesel pusher with a high pitched whistling sound coming from the front end. It is intermittent depending on the outside temperature, cool weather makes it worse. It occurs between 50 and 60 MPH. I've checked everything I can think of but cannot find a source.