My car started making a noise at 70-80 mph. Is there anything spinning in the speedo that can cause this (speedo cable, gearbox?) So far I cant tell if its a wind noise or the speedo. I did just change the cabin air filter but the noise happens with the heat/ac off also?

 

I think the first step to diagnose any squealing in the dash is to turn off the swinging center air vents and see if the noise goes away / changes.

 

its not them, I turn the whole heat system off when I first heard it. It sounds alot like a whistle or a bearing going out, it goes up/down in pitch. It also never starts before 70 mph, and I havent driven much over 80.

 

is it possible that it may be coming from the windshield? failed seal where the dash is.

 

Besides a wind leak at speed it could be mechanical. Also make sure your inside cabin filter is clean and your outside vents are clear of debris.
This may be out of date advice - with a mechanical speedo cable - the cable is spinning faster inside its housing as you increase speed. Sometimes these went bad and had to be replaced if they could not be oiled to make then run quiet, But I'm not sure if the LS even has a mechanical speedo cable - it may be all electronic/digital.

Can you get or borrow a stethoscope - that might help locate and diagnose the problem.