My interior fan suddenly started making a LOT of noise. It vibrates so much, I can't hear the engine over it. It is directly related to the fan speed and doesn't matter if A/C is on or heat is on.

Anyone run into this issue before? Any tips?

 

Replacing the fan is suposedly pretty involved....
My fan made some squeeling/screaching noises a couple years ago...
My solution was to lube it up....went away.
Hard to reach, but possible.
remove the filter on the passenger side....and I did it 2 ways...with long extention tube on spray lube (like 2-3 times longer than the freeone), and some on a finger....it is hard to get to....I was reaching in up to my sholder, bent like a monkey...but if you feel around you can determine where it needs lube. Hopefully this works for you.
I used mobil 1 spray lube (good stuff, but I think it no longer made, and some lithium grease (thiner stuff from a can, sprayed on a finger, then applyied by hand)....after about 5 or 10 minutes of running the fan, the sound and lingering smell wentaway. Been a couple of years now.....