I noticed a "humming" noise in a kind of off-on-off-on manner, when I drive over 65 mph
it's like 1 second humming, 1 second off, 1 second, 1 off .... and so on. it has Firestones tires. I did alignment, bearing checking (no problems) balance and tire rotation, still didn't help. If the car on park and step on gas to high rpm no humming, its only happens when oh highways over 65mph, humming on/off will be in faster pattern, till I can't to notice it on 80mph I guess because the high road noise on that speed.
My car has an automatic transmission.
A "humming noise" while driving at speed can be caused by tires or wheel bearings. If you drive with the window open and you hear the noise outside the car, like the sound bouncing back at you from a wall, highway divider, etc, then it’s most likely your tires.
Also, if you run your open palm across the tread surface of the tires and you feel a choppy pattern, like if you made a fist and ran your opposite hand across your knuckles, that’s another sign that the noise may very well be from the tires.
When driving with the windows closed, if you hear the noise change volume or pitch when say, changing lanes, then it it most likely one or more wheel bearing.
If you’d like to get this fixed, consider YourMechanic, as a certified technician can help you diagnose the source of the noise and make the necessary repair. Good luck.