2004 Dodge Ram cold weather howl

[RamMan04]

The temperature in Oregon has dropped into the teens. With that, came a howl from the engine compartment. I have the 2004 2500 Dodge Ram 4x4 with the cummins 5.9. After the truck warms up to 180 degrees, the howl goes away. The howl is noticable at accelleration. But more so on decelleration. Does anyone know what is causing this?

[OldGuy]

I also live in Oregon at 5000 foot level. My 01 2500 turbodiesel had same howl last winter. Ex Dodge Dealer mechanic checked my Power Steering fluid level which was low. Since topping it up with Mopar Power Steering Fluid and plugging in overnite before startup, I've not had the howl since. Temps here have been 0-F at nite.:)