Hi..Humming in rear of car when driving at
any decent speed.. it gets louder as mph goes up.
The mechanic had the car on a lift ran the car and heard no noise and thought it was the tires.
We got oem size tires Bridgestone Alezia and after install humming still there. Front very quiet rear is humming. Disappoint to not have solved it at cost of $1251. Last year the rear bushings were changed and all diff oils changed..year before Timken bearings done in front.
It almost sounds like a less obvious version of the noise when our front bearings needed replacing.
Any idea what it is ?
The car has 205k miles on it we have owned and taken care of it since 23k.
Many many thanks for your advise over the years.

 

There’s not much back there to cause humming noises.

-Rear diff (how was the oil when changed?)
-Wheel bearings (easy enough to inspect)
-Rear drive shaft (this tends to cause vibration when bad)

Bummer about the tires…

 

I didn't see see rear diff oil ..he did all of diffs over a year ago he probably won't remember.
Car has 204k ish miles on it none of the 3 parts you listed have ever been replaced in all that time.
He had it on the lift and ran it and heard no noise..so the noise is happening while under pressure. Would diff be making noise while on lift
or while under pressure ?
More accurately it is like a propeller sound in rear while on highway.
Please advise.

 

One would have to assume the diff oil was clean (no substantial metal) when drained or it would have been obvious. We cannot rule it out, but it is the least likely (not a wear item) and it is the most expensive.

So let’s focus on the wheel bearings and rear drive shaft (also called the “prop shaft”). Bearings will be least expensive and most likely for a humming (they are a wear item). This would also be most likely to make no noise while on a lift, but cause humming while loaded on the ground. A bad drive shaft would not experience a change in load when on the lift or on the ground since it doesn’t carry weight from the vehicle.

All that to say, look into the wheel bearings next. That’s what I would do.

 

Lovely thank you so much for looking into it.
We just came back from Henri the mechanic who sat in the back of the car and my wife sprinted us around and he says he mostly hears it on the back right passenger side but he will change both sides..He doesn't think it is the differential either or it would be coming more from the middle he said.
Many thanks to you once again.
The rear bearings have gone on for 200,000 milesa good service life..thank you Land Rover Ford

 

When driving, drop into neutral. I doubt its the drive shaft but if it is or even the rear diff there will be a noticeable change. No change in sound, it is the rear bearings. But since he is going to change em, well my guess is problem will be solved. I did mine at 180k or about out of preventative. 200k is plenty on the rears! Fronts usually dont make it past 150k miles.

 

Will do thank you.