Can't diagnose rumble/growl...going insane about to drive off a cliff

After weeks of research/troubleshooting, I can't stand it anymore, so I have to ask for opinions.

Here's the deal..
I have developed a rumble/growl. It's somewhat faint and others who ride with me don't notice it, but it is clear to me. Hard to pinpoint from where, but it sounds like it's in the front. Heard best from 5-40ish mph, most notable at slower speeds, particularly while coasting/slowing/braking (present almost all the way to a stop). I believe it is still there at higher speeds, but gets lost in road/wind/highway noise. Seems to match wheel/road speed (but does not increase in pitch/tone), pulsating/rhythmic sound, can feel it in the floorboard, independent from transmission gear or engine load. I'm lifted 2.5" 8+ months now with 80k miles on the truck...noise is new ~1.5 months ago. I just suddenly noticed it while driving to work one day. Sound/vibration has not changed/worsened since discovery.

Here's what I've done/checked since discovery:
-All boots, bolts, linkages, suspension look/feel fine.
-Front diff fluid changed: was 1/4 quart low, oil looked fine, small amount of fine shavings on drain plug.
-Both rear wheel bearings replaced.
-Rear diff fluid changed: was a little (~1/4") below full, more fine metal shavings on drain plug (2nd oil change), oil looked fine.
-Tires rotated, no obvious tread problems.
-New front brake rotors. Drum brake shoes in rear looked fine.
-Driveshaft carrier bearing looked fine, U-joints all looked good and well maintained.
-Truck driven without rear driveshaft with no change.
-Does not change in 4WD.
-Still there regardless of driving on sand, asphalt, dirt (I had almost convinced myself it was tire noise).
-Had my brother drive by me while I was standing outside and I couldn't hear anything on the exterior.
-Did a 500+ mile road trip. Upon returning I immediately put a heat gun on the rear diff (154 degrees F was hottest I could find). Checked drain plug on rear diff and there was a very small amount of very fine shavings on the magnet.
-No play in driveshaft/rear differential connection.
-Rear diff breather was rusted shut, did diff breather mod.
-Front diff breather appears to be functioning properly.

And here's what else I've done in the last 8 months:
-LR SPC UCAs
-New LCAs and bushings
-ECGS diff bushing
-Both front wheel bearings replaced with Bama bearings.
-poly body/radiator mounts.


I am at a loss. Does anyone have any ideas? My only thought is that maybe it is indeed the rear differential making that noise/vibration. But I see no reason why that would be going out already. Or could it be the manual transmission?

Thanks,
jib

 

Man I hope you get this figured out... makes me rethink my concern with the very slight noise I hear occasionally. Sounds like you're one of the few people who actually read every other thread and took all the advice before posting. I'm curious to see what the experts on here say. Good luck!

 

Could be a bearing noise in the front .. even tho they're new..

Lift the front wheels off the ground, grab the upper control arm and spin the wheel. If the bearing is rough you'll be able to feel the roughness with thehand that's on the control arm

 

Could you possibly get your hands on another set of tires on rims to swap on and try?

I'm assuming and alignment done after lift and front end work?

Diff issue will change with load, transmission issue will change with gear and/or load.

 

You might wanna have this looked at. If you've found metal shavings in the diff TWICE I wouldn't ignore it.

I've got an aftermarket 3rd member (rear diff). Had the pinion bearing fail (which causes noise, vibration) and caused the pinion to move laterally into the carrier and also chipped a tooth on the ring gear.

Gear oil was practically crystal clear. But there was quite a bit of metal shavings...

 

Wow, third pic looks like metallic paint basecoat! That is some finely ground steel pigment!

 

Noise/vibration persists. I checked both diffs again and magnets are clear. Just put in new gear oil in the tranny, the old stuff was pretty dark. Went by discount tire, they balanced all tires and didn't see any cupping. I lifted front up and spun both wheels. There is some scraping of the brake pads, but no bearing noise and no vibration felt in UCA. No play in wheel grabbing at 12 and 6 either. Noise does not change while turning, unless I make a super aggressive turn, but it is same in both directions. I went to a 4x4 shop here in Denver and the owner drove my truck with me in it. He had a hard time hearing/feeling it at first, but confirmed there was something there. He didn't think it was differential related. When I have the energy I may lift the front again and take off the wheels and brake calipers to really get a good listen with a stethoscope. It does sound like some sort of bearing noise. But I think I'm about at the point where I'm just going to turn the radio up and drive it until it gets louder or something breaks.
Thanks for the input.

 

Any update with this I am actually having what seems to be be same noise/issue!? I'm driving a Toyota Tacoma 2012 trd off road. Shop told me my rear differential needs replacing and possibly rear axles?! Not sure if I should go to a second opinion I am In Denver, Co as well.

 

I have a video of the noise my truck is making But having trouble uploading it let me know if you want me to send it

 

Have you isolated engine related noise by coasting with the engine off? Bearings in idler pulleys, alternator, and water pump could be faulty. How did you check the carrier bearing? You would have to remove the bearing out of the carrier assembly to check it. After the 500-miles trip, was the noise louder or the same? Hope you find the cause.

 

A carrier bearing failed will not be noticed by inspection. You can spin it fast enough while on the truck to feel that it's bad.

I changed mine because it was the only thing left to change and I was sure I was wasting time and money.

Even spinning by hand it felt normal. I cut it apart with a thin disk. There were small lots of delaminated chrome on the race.

 

Having what I think is the same thing. Just did a 150 mile trip mostly uphill, 2015 manual TRD OR, and floored for most of the way in 6th, got to my destination, came to a stop, and noticed it when slowing down. Have a 3" leveling kit in the front, and non-oem leaf springs.

 

Even though you checked and replaced it. It could still be your front wheel bearing. It makes a rumbling sound at low speeds but when you drive faster it’s not as noticeable. Even in 4wd you still hear it so my guess is the front bearings are defective.
Also if you changed tires, the sound might be the tires too but I’m still going with front wheel bearings.
Are they press in bearings or can you replace the whole unit? If it’s the whole unit you can easily try another set yourself.