drone that comes and goes randomly

[battery1882]

Hey guys,

Need some expertise on low frequency noise that's driving me crazy.

I've searched for days but could not find anyone with a similar issue.

Basically, there is a noise coming from underbody. I think it's around center area, but could be completely wrong.

I was thinking maybe it was one of the wheel bearings, but it comes and goes very randomly; regardless of throttle input, brake input, and steering input. it will do it going 10mph through 75mph (haven't driven faster than that).

Sound is impossible to duplicate as it's completely random.

It sounds like surface of the road changing: going from asphalt to concrete vice versa. Not really loud but it would be quiet and all of the sudden feel like going though a old rugged asphalt then back to quiet.

I've changed : all fluids, front brake caliper/pads, shocks/springs all around.

let me know if you guys have any suggestions,

 

[runnyrunnerton]

When diagnosing a hum, i try and hear if its a wave interference hum or a single note hum. Wave interefence is the tuning a guitar effect open string and fifth fret on string below. two notes fighting for the same wavelength. Its the wuuuuuuuu wuuuu wuu wu wu wu wu effect. pulses faster then slower. Like a bell curve.You can pick it up on airliners when they engines rpms match up.

This is one of those hypersensitive sounds only you can hear from your truck as your used to it, but its there. Its usually tire noise, and some component holding them on track, is slightly allowing them to run up and down some scale of "WRRRR" when it gets close to another tires' "WRRRR" noise you will hear it however not usually under 30mph for me.

Wave interference is almost impossible to track down in one sitting, I rotate my tires fairly often to avoid just such a thing as I cant unhear a rattle or a hum. Even treads minimize previously mentioned "WRRRR"

Make sure its not this, then slide underneath your truck and start striking stuff with a rubber mallet and look for loose parts. Especially since you just changed out all kinds of parts, Put a wrench on every bolt you touched during the improvements, LUG NUTS are in this group of must checks.

Then google some common noises. Bad wheel bearings (MY BEST GUESS if its not tire noise) Rear End Going bad, U-Joints Failing, Transmission Whine, Torque converter bad etc. Happy Hunting

 

[Lunarphase]

Try lubing the drive shaft?

 

[diverscale]

greasing the driveshaft as mentioned up there is the easiest option to try.


Then I would rule out the some options by putting the rear on jack stands and removing the wheels. After being secured, 'drive' the truck through the speeds where you hear the drone. You still hear and feel it?

If still there, remove rear drive shaft and drive on 4X4 with front drive shaft only. Then we will be able to help you after these different steps and results.

 

[battery1882]

Thanks guys,

I forgot to mention that I did lube all the zerk fittings previously with no change.

It makes noise both in 4WD and RWD so I assumed FWD mode would make noise as well. Wouldn't that be the case?

Last night, I changed, front rotors, rear drum, shoes and tightened sway bar bushing bolt that was loose.

Nothing changed.

I really appreciate your comments.

 

[battery1882]

Recorded the noise yesterday.

I don't think wheel bearing would be intermittent like this..

Anyone with similar experience?

 

[battery1882]

In case anyone is curious,

I put chassis ears all around and found that it was coming from the driver side rear.

Wheel bearing was done.