Got something weird going on I can't figure out. Very occasional noise that shows up, every 5 miles or so at 60mph on a straight road I get this intense growling/grinding for a few seconds. I let a frequency analysis program run on my phone and when it the noise happens I get noise at 100Hz (maybe, that's also firing frequency of the engine but it gets more intense), 200Hz, 300Hz, 400Hz. Wheel speed at 60mph is 10Hz. The intensity varies if I wiggle the steering wheel while it's happening. It will do it in 2wd or 4wd auto, no difference so I don't think it's the 4wd shift collar and from pictures I can find, I don't think there are exactly 20 teeth on those anyway. I replaced the drivers side unit bearing last night, did the passenger side last winter. Did the same noise on the way to work this morning again. I'm going to try to get a video with audio of it but it's really sporadic. 310k miles, rust free, never had any other issues. Doesn't sound like an abs/stabilitrac thing.
Thoughts?
Thoughts?