NEED HELP Reverse Whine ... ???

[AC75TB07]

Sometimes when I shift into Reverse and hit the accelerator, I hear a low whine sound... Not extremely loud or but enough to bother me...

I think it's from the rear of the truck but hard to be exactly sure. I've had my front and rear differential fluids changed in the last year, and there's no transmission or shifting issues that I've noticed. The sound is never there when in Drive.

Any ideas?

2007 Trailblazer LT ~120,000 miles.

 

[mrrsm]

From TV:

Tranny makes whining noise when cold and when put into...

www.trailvoy.com

 

[AC75TB07]

I hope it's not THAT!...

Today I took the truck to an empty car park and put it in reverse while holding the door open so I could hear the sound better. It sounds like it's from the rear, and more like something grinding or making contact where it shouldn't - probably from the driver side wheel.

I'm sorta thinking it might be something to do with the dust shields... There's a slight scratchy scraping sound when going forward too but at higher speeds it's less noticeable. Sorta a different sound than when in reverse but from the same area...New pads and rotors last year.

Gonna have to get up under and take a look, see what I can find... when it warms up...ugh!

 

[Mooseman]

I had an issue with a rear brake pad shim rubbing on a rotor. Wound up replacing the pads and rotors to eventually get rid of it. You could certainly start there, then open up the differential. Not a bad idea to do a tranny service too once it warms up. Don't forget the front diff and that the transfer case needs its fluid changed every 80k km with AutoTrak II fluid.

 

[AC75TB07]

It sounds more and more like something from the wheels making contact where it shouldn't to me. I did just have my front differential and transfer case fluid changed in October, and the rear differential fluid last summer, so those should be OK.

 

[Blckshdw]

Maybe try lifting the back end, and putting it on jack stands. Set the tranny in neutral, and turn each wheel by hand. Should be easier to pinpoint, if it's literally in front of your face, and no engine noise to get in the way.

 

[AC75TB07]

Thanks, that's a good idea. It's meant to be a little warmer next week, I'll give that a try.

 

[AC75TB07]

Just thought I'd update this... the problem is the emergency brake. Didn't tear it apart cause I don't use it and really don't care about it, but with the truck on a ramp spinning the wheel, the noise comes from inside the rear wheel drum. Not from the regular pads or rotors.