Rear end moaning, not wheel bearings.

[iranmeba]

I recently changed both of my rear wheel bearings due to excessive noise and play. During diagnosis I jacked up my rear end and spun the wheels using the engine (one at a time) both were noisy/humming so I changed both. While doing this test there also sounded like there was some noise coming from the diff area but I wasn’t sure since the wheel bearings were so loud on their own.

After the install I repeated the test, wheel noise is gone but the rear noise is still very present. It’s almost like a roaring howl/moan, goes up with wheel speed. It definitely sounds like it’s coming from the rear center of the car but there are a lot of moving parts back there so it’s hard to tell exactly from what. It’s not engine or tranny as while testing I spin the tires to about 70mph, throw it in neutral and turn the engine off, and then go back and listen as the wheels spin down.

Anyone experience this before?

[Muzz258]

The noise is likely to be the spider gear in the diff working really hard. With one wheel on the ground and the other up in the air all the driving force is going to the one wheel in the air. The spider gear need to transfer all of the drive to the one wheel, so they are spinning at maximum speed. Something they don't need to do in real driving conditions as they only work to balance the difference in wheel speed when going around a corner

[iranmeba]

thanks for the reply Muzz258. I suspected that exactly what you described might be causing the issue, specially since I pretty much cannot hear the noise when I'm actually driving but I wasn't positive since I didn't recall hearing that noise the first time I did the same test 10 years ago, but granted that was a long time ago. I've done all four wheel bearings at this point (the fronts were totally trashed even though I couldn't tell they were making noise) and the car is driving and sounding great now. I'll leave this alone unless I start to get more weird noises.