Attention: TDR Forum Junkies 
The noise is akin to a turbo boost, but without the whine. It's more like a push of air from a compressor.
This just started a couple of days ago, when our temps dropped below 0 and have stayed there.
Last night, when it started again, I noticed it was right near the 1700 RPM mark, if I let off the accelerator, it went away. But then started again as soon as it hit 1700 RPM. So, I tried it with OD off at 1700 RPM and it still did this.
Is this maybe a specific occurence related to extreme cold? Before I forget, the truck gets a minimum 15 minutes of warm up time with the auto transmission in neutral before it moves, also stored in a heated garage overnight, every night.
This just started a couple of days ago, when our temps dropped below 0 and have stayed there.
Last night, when it started again, I noticed it was right near the 1700 RPM mark, if I let off the accelerator, it went away. But then started again as soon as it hit 1700 RPM. So, I tried it with OD off at 1700 RPM and it still did this.
Is this maybe a specific occurence related to extreme cold? Before I forget, the truck gets a minimum 15 minutes of warm up time with the auto transmission in neutral before it moves, also stored in a heated garage overnight, every night.
