About a month ago my trailblazer developed this new features. When you get into the car and start driving, everything feels completely fine. Then after about 5 minutes you start noticing slight vibration (very slight, just feels like something isn't quite right). After about a 20 minute drive, the vibration is very noticeable. By that time, it almost sounds like low engine rumble, but its pitch and volume vary directly with car's speed, not engine speed. When it gets to that level, it is also easily felt in the steering wheel.
Three weeks ago, I jacked the car up and noticed that there was a ton of grease spewed around passenger side CV boot. So I went through the motion, which took a while for various reasons, of replacing passenger CV shaft and while in there, also rebuilt 4WD disconnect with fresh bearings and seals. Yesterday I put the car back on the road and the vibration is still in there unchanged.
I tugged on both wheels to check wheel hubs and at first glace the wheel bearings appear fine. I've had bad wheel bearings on this car before, left one is 5 years old. right one is 1 year old. Whenever wheel bearings were bad a) vibration would be constant through out the drive (i.e. you can feel it the second you start driving) and b) they would change in sound when turning left or right.
This current vibration is... 1) unaffected by turning left/right or going straight 2) does not change in sound if 4wd is engaged or disengaged 3) unaffected by putting the car in neutral and revving the engine
I also checked the front differential fluid level (obviously destroying the fill plug in the process) and topped off the oil level. It was a little low, but no where near empty.
Any ideas what would be causing it?
UPDATE: Drove the car to work today. I have to take back (1) from above. If I turn the steering wheel right, vibration becomes stronger and if I turn left it gets weaker, which is actually consistent with driver's side wheel bearing being bad. The difference is that with my previous bad bearings, I only had to apply slight pressure to the steering wheel to hear sound difference, but this time, I have to push the steering wheel a bit further out (can still hear difference in a single lane going straight). Also the vibration this time seems to be distinctly lower pitch than the ones I've heard in the past with wheel bearings, but maybe they come in different shapes and sounds?