OK. Now my truck is making this noise. About 5 seconds in. It happens twice. It's kind of a whirring sound.

You feel it through the pedal. Happens on smooth & rough roads. In neutral or drive. Regardless of throttle.

What do you hear? (Not the zipper or blinker sounds) BTW it is 10°F & plenty of snow and ice.

https://youtu.be/6uHPoVkmYPA

 

I mainly hear the zipper and blinker noise, but the most common whirring noise is the fan clutch that has gone bad and the fan is engaged constantly. Sounds like a loud vacuum cleaner. Try moving the fan when the engine is off and cool. If it won't move...time to replace.

 

Will do. But could it generate enough vibration. To be clearly felr. Through the gas pedal?

 

make sure mud(dried) not stuck in fins, fins broke, blades bent/broke/chunked

 

I don't know about through the gas pedal specifically, but I had an '83 F150 with a recently rebuilt 302 (3000 miles); the previous owner reused the old fan clutch & the engine vibrated inconsistently.
The fan was able to move sideways about an 1/8" or so due to the worn clutch hub, causing the vibration - but sometimes it sat almost central.....so no vibration.

 

I'll check it out.

 

If you are suspecting the fan/clutch causing some kind of vibration you MIGHT be able to remove them and drive with them off for a short time (so as to not overheat your engine) and see if by eliminating them that gets rid of this mystery noise/vibration thing. Again I don't recommend doing it for too long because of the risk of overheating but if it's for a few minutes after you cold soak it (and in colder weather) you'd probably be ok.

 

Nice idea. Will keep it in mind.

 

The fan moves fairly freely when engine is cold.

 

ABS may be the issue. It sounds like the LH side. Given the facr it has rear wheel ABS. Maybe that is firing at random times??