Faint whining noise from the back at highway speeds...

[Emilbadal]

Hi everyone,

Recently, I have changed my job and my commute is around 110 miles round trip. After a month in my new job, I noticed a kinda faint whining noise which is mid to high in pitch. I cannot pinpoint it where exactly it's coming from other than it's coming from the back. I was suspecting the wheel bearings going bad , so I decided to do the do some tests. I jacked up the rear, and did the shaking test in nuetral and parking brake disengaged both ways(up Down and side to side). No slack whatsover. I did the spin test and listening to any kind of whirring sound from the bearings, still nothing. The only noise I hear is brake pads on the discs. Since turning the rear wheels in nuetral is very difficult, I turned on the car and put it in gear and let it spin the wheels. Still nothing, other than the brake pad noises. After that I test drove the car suspecting maybe the rear calipers are acting up maybe and they are scarping the pads on rotors, however at highway speeds regardless of me braking or not or steering side to side, the noise stays consistant and doesn't change which tells me that the brakes are not the culprit either. It is perplexing me a bit, because I've never tracked my car and never have done any burnouts or donuts ever. At this point I am only suspecting that it might be my differential, but that also seems premature failure at 26K miles. I'm wondering if anyone has had this kinda issue and could shed some light and provide some guidance.
Thanks in advance

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[Ogopogo]

Wheel bearings are more likely to growl so I suspect that is not the case. A high pitched whine is often more associated with gears, such as the differential. There should never be an issue with the differential in a vehicle with standard use, but as a starting point, I would have the differential gear oil checked for fluid level and fluid sample analyzed for contaminants, fine bits of metal for example.

 

[Zrussian13]

I have to agree with checking/ replacing the diff fluid first off. I had a rear wheel bearing go bad and it lit my dash up like a Christmas tree long before you could hear or feel anything.

 

[Emilbadal]

I totally agree, I'll change the diff fluid this coming weekend. Any recommendations on what weight and brand I should use?

 

[Zrussian13]

I used royal purple maxgear. Good luck figuring out the whine!

 

[andrewtac]

Does the frequency of the whine change with speed? Sounds like diff whine.

 

[DougS550]

A whine usually means diff gears. Since it is in a OEM gears, the oil analysis should shed some light on narrowing down your issue. If no excessive metal found in diff, a High end Full Synthetic just might quiet it down if not, check diff gear clearances that would be my next guess. Good luck.

 

[Zrussian13]

Just thought of something. If you have a torsen diff I believe you'll need friction modifier when you do your fluid change. Check the manual for how much. I don't remember off hand.

 

[DougS550]

Just thought of something. If you have a torsen diff I believe you'll need friction modifier when you do your fluid change. Check the manual for how much. I don't remember off hand.

I am sure when he picks up his Rear Diff Oil that he will verify if an Additive is needed.

 

[Zrussian13]

I am sure when he picks up his Rear Diff Oil that he will verify if an Additive is needed.

I would hope so but it can't hurt to remind him. We've all overlooked something simple in our lifetimes at some point.

 

[DougS550]

I would hope so but it can't hurt to remind him. We've all overlooked something simple in our lifetimes at some point.

Hell Ya and any mechanic who says he hasn't made a mistake, Is a Mechanic you want to stay away from. Case in point. I have been wrenching on my cars, race cars, motor cycles for decades. I currently take care of 6 cars for my family. I didn't realize except by mistake that a CVT Transmission fluid is actually more like engine oil (Brownish Color and is a thicker viscosity than ATF which is Red) and needs to be replaced every 15k or so IAW OEM Manual. I never even gave the CVT another thought for I thought it had the same ATF fluid as every other transmission I've worked on where the ATF will last 100k before changing (Normal Driving cars). I just changed my wife's CVT fluid at 61k and it smelled like you would expect if you ran your engine oil for 60K, Burnt. BUT Fortunately, it has no issues, runs smooth.

 

[Emilbadal]

Does the frequency of the whine change with speed? Sounds like diff whine.

At low speeds it's almost non-existent but at 55+ I can clearly hear it.

Just thought of something. If you have a torsen diff I believe you'll need friction modifier when you do your fluid change. Check the manual for how much. I don't remember off hand.

I don't have a Torsen but I think I will still need the friction modifier, unless it's included in the fluid I'm getting. Haven't decided which brand to buy yet...most likely will be Royal Purple because it's available in store nearby and online places are not any cheaper anyways.

 

[andrewtac]

Sounds like gear if it increases with speed.

 

[Ogopogo]

At low speeds it's almost non-existent but at 55+ I can clearly hear it.

I don't have a Torsen but I think I will still need the friction modifier, unless it's included in the fluid I'm getting. Haven't decided which brand to buy yet...most likely will be Royal Purple because it's available in store nearby and online places are not any cheaper anyways.

If the whine goes away, it was an oil issue. It wouldn't hurt to have the old oil analyzed for contaminants to reinforce that was the issue.
https://www.autoblog.com/2016/01/07/symptoms-of-bad-or-failing-differential-gear-oil/

 

[Emilbadal]

Any recommendations on the oil weight? I'm inclined to use 75W140 for sake of a bit more protection and more noise suppression. What do you think?

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