Humming noise near the left rear - only from 60-100 km/h

[SureshR]

So yeah that's the symptom .. it is most audible during 60-100 kmph (or maybe the engine growl just drowns it out at higher speeds). Ford Endeavour (aka Everest in Australia, SUV body on a F150 type vehicle, with the 3.2 L5 diesel), run 135,000 kilometers.

Draining the oil in the rear diff didn't throw up any metal shavings or similar, so once drained, fresh 80w90 manual transmission fluid anyway got replaced in it, as the manual specs. Disconnecting the prop shaft to disable AWD and spinning the rear wheels doesn't show any obvious bearing issue.

Anything else to check before stripping everything to get the bearings inspected?

Edit - the vehicle had rear link rods and shocks recently replaced.

 

[vavavroom]

It could be a wheel bearing in the early stages of failure.

 

[SureshR]

It could be a wheel bearing in the early stages of failure.

Yeah that's what I still suspect. Replaced the front wheel bearings which were worn but functional, proactively. The rear wheel bearings are rather expensive, and then some of the bearings, if they fail, would involve changing the axle itself .. such as the parts tagged orange and green / purple here. If it is just the crown bearing or its oil seal, then fine. Not as expensive as changing the axle at any rate.

135k kilometers (~ 84k miles) is somewhat early for a bearing failure even in its early stages though.

 

[B1974]

Could be a bearing or even a bad tire. I'd rotate the tires first and see if the noise moves.

 

[SureshR]

Could be a bearing or even a bad tire. I'd rotate the tires first and see if the noise moves.

The tyres needed and were due for rotation, alignment and balancing. The noise has reduced but I think is still there, a little. I will need to test this on a highway to make sure.

I had done this balancing not more than a thousand km back btw but doing a fresh round of this showed substantial (4 degrees or so) deviation in the toe, suggesting the previous alignment centre might have messed up the job.

Thanks! Let me test this and see.

 

[Delta]

I had an older 2nd gen Tacoma do this. Very similar symptoms. First sign of what happened is changing wheels/tires I noticed gear oil on the outside of the DR drum. Seal leaked and took out the bearing. Noise progressively got worse and a broader speed range. It is a very similar style 3rd member/bearing setup. Kind of a PITA and the guy who did the work even broke his press.

 

[Ranger83]

Find a big parking lot and make figure 8’s. If it’s a lot louder when that wheel is on the outside, bearing time.

 

[xspeedy]

Do you have a temp gun? After a long drive see if the left is hotter?

 

[vwmaniaman]

Sounds like a wheel bearing to me.

 

[KrisZ]

Jack up the rear on one side, chuck the front wheels, fire up the engine and put the car if drive or reverse. If it’s a wheel bearing, you will hear it right away.

Of course, use your own judgment and do it at your own risk.

 

[SureshR]

Do you have a temp gun? After a long drive see if the left is hotter?

Marginally warmer to the touch but I could be wrong and India is a rather hot country.

The tyres (Michelin LTX Trail AT tires, 285/60R18) had uneven, patchy wear for all 4 - and this seems to have developed in the last 10k or so of driving it. Alignment knocked off around 4 degrees on the toe as well.

Maybe an artefact of the car having had its camber bolts, front lower arms and rear link rods / shocks replaced during the lifetime of these tyres, but they ran barely 38k km / 23k miles so far . Would bearings going bad also cause this?