Hello,
I made a post about a week ago on a vibration/humming my wife's 1999 Sentra GXE was making. Link to the post here:
http://www.nissanforums.com/showthread.php?t=106891
Found out what the problem was. Rear passenger-side wheel bearing was shot. When the car was up on the lift, none of the wheels wobbled when shaken and they all turned smoothly. It wasn't until I took the wheels off and spun the actual hub that I discovered the problem. While I was replacing the brakes, I noticed that when I spun the hub it turned pretty rough. It felt like the volume knob on the factory radio, you know, bumps up to the next notch but not a smooth continuous motion. The driver's side was fine and spun freely. Bought a Timken for $62 at a local parts shop and the noise is gone. My best guess as to the type of noise it was creating is that, although it was groaning throughout the whole speed range, at specific speeds there were resonant frequencies due to the interior cabin size.
Anyway, thanks for the input and for a place to vent. If you ever get the wah wah noise, check the bearings if rotating and balancing the tires doesn't take care of it.
-Johnny-
Linear Mode
