Squeal when going backwards!
 

I've got an '09 MT, 78K miles. Regular oil changes and brakes, even new rotors on front only.

About a week ago, I started noticing a harmonic hum, or squeal, from the rear when I go backwards ONLY. Doesn't matter whether I'm just gravity-drifting backwards or under power, I hear the noise. Doesn't matter whether parking brake has been applied before or not, hear the noise. Speed backwards doesn't affect the pitch, but more speed "seems" to give a slightly louder noise.

Sounds like it's coming from the passenger rear, but am not fully sure. Can't see anything obvious on rotor from the outside, but I haven't yet gotten it up on friend's lift yet for a closer inspection.

What's got me stumped about this is that it's ONLY when moving backwards. Absolutely no noise whatsoever moving forward.

My friend is worried it might be boots or bearings or even the diff, but before we go off the deep end ;) I thought I'd check with the knowledge base here and see if anyone else has heard something like this before. Appreciate your thoughts, thanks!

Nothing that I can think of...

How fast are you going in reverse!!! ;)

But yes, a closer inspection is needed.

Plz report back.

A lot of times the squealer tab on a brake pad will initially touch while going in reverse long before it does going forward. It could be that simple. Not sure why it does. I have seen many different vehicles act like this.