Car makes horrible "humming"? noise when backing up

[SarcasticDwarf]

My truck has been making this noise for the past couple years. Two mechanics have been unable to figure it out. To me (who knows nothing about vehicles), it almost sounds as if rubber is rubbing. If I accelerate hard (in reverse), it will stop. If I have driven it for half an hour, it won't do it (usually). One mechanic said that is just the anti-lock brakes coming up, and that it was nothing to worry about. I would not have a problem with that if it were not for the fact that people 100+ feet away turn and look to see what the noise is. Anyone have any ideas?


Note: 97 Dodge Ram 1500 2WD. New tires on it, the noise happened long before the new tires. Automatic.

 

[Heisenberg]

Is it a manual or automatic?

 

[SarcasticDwarf]

Originally posted by: Heisenberg
Is it a manual or automatic?

Sorry, automatic.

 

[iamwiz82]

What if you drive backwards for a while? Does it stop?

 

[Cattlegod]

do you have a camera or something to record the sound?

edit - is it related to wheel speed? i.e. the faster you go the higher frequency the sound gets?

 

[SarcasticDwarf]

Originally posted by: iamwiz82
What if you drive backwards for a while? Does it stop?

I've never tried driving in reverse for an extended period. The longest I have gone is about 150 feet. IIRC it does quickly stop sometimes, even if I do not accelerate hard.

 

[SarcasticDwarf]

Originally posted by: Cattlegod
do you have a camera or something to record the sound?

edit - is it related to wheel speed? i.e. the faster you go the higher frequency the sound gets?

No camera or such to record it at the moment. The sound does not seem to change significantly.

Gotta run some errands, bbl.

 

[Heisenberg]

I think this is going to be really hard to figure out over the internet. I'd suggest having somebody back the truck up while you stand next to it and listen for where it's coming from.

 

[iamwiz82]

It could be surface rust on the brakes.

 

[Rogeee]

From experiance I am going to guess that it may be either sticking shoes in the rear breaks (drum brakes are self energising,the shoes cam outward when applied) or it may be excessive backlash in the ring and pinion gears in your rear end.

 

[Fiveohhh]

I'd suggest not driving backwards.