Possible differential noise?

[lzaffuto]

Taking my car to the dealership tomorrow to have it looked at. I'm getting a intermittent "humming"(sounds like a constant woooooooooo when it happens) coming from the rear. I mostly hear it at about 30ish to 40ish mph when in traffic with my foot barely on the throttle (like just keeping up with the car in front of me). It gets about three times louder when in the same circumstances as above if I start climbing a hill. It either goes away or I can't hear it anymore if I press the throttle down harder and especially if the car downshifts to a lower gear. Also goes away when coasting or braking. No vibration attached to it that I can feel, only noise.

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[Cobra Jet]

Taking my car to the dealership tomorrow to have it looked at. I'm getting a intermittent "humming"(sounds like a constant woooooooooo when it happens) coming from the rear. I mostly hear it at about 30ish to 40ish mph when in traffic with my foot barely on the throttle (like just keeping up with the car in front of me). It gets about three times louder when in the same circumstances as above if I start climbing a hill. It either goes away or I can't hear it anymore if I press the throttle down harder and especially if the car downshifts to a lower gear. Also goes away when coasting or braking. No vibration attached to it that I can feel, only noise.

If and when at speed, if you safely put the car into neutral - does the sound or feeling still exist?

 

[GT Pony]

Could be the differential if the noise changes under different load conditions. First thing I'd do is check to make sure the fluid level is full.

 

[lzaffuto]

If and when at speed, if you safely put the car into neutral - does the sound or feeling still exist?

Good suggestion. If they tell me it's "normal" tomorrow I'll try it. I'm thinking it will go away in neutral because it goes away as soon as I take my foot off the gas pedal - when it happens throttle on gets noise, throttle off no noise - I can do it rapid fire like pulling a trigger.

 

[lzaffuto]

Could be the differential if the noise changes under different load conditions. First thing I'd do is check to make sure the fluid level is full.

I thought about just going out and getting Royal Purple differential fluid and changing it out just to see what happens, but then I thought because it is under warranty if I still needed to take it in after changing it if they found something wrong in it they would say it's because I changed the fluid and deny the warranty claim. I will probably go this route if they tell me that it's "normal", just for my own peace of mind that I've done everything I can to prevent a failure.

 

[GT Pony]

I'm thinking it will go away in neutral because it goes away as soon as I take my foot off the gas pedal - when it happens throttle on gets noise, throttle off no noise - I can do it rapid fire like pulling a trigger.

So you can't detect any noise coming up through the stick shift? If not, then it must be the differential gears.

 

[lzaffuto]

So you can't detect any noise coming up through the stick shift? If not, then it must be the differential gears.

Well, it's an automatic, but yes the noise is definitely coming from behind me, not from the center console or front. The only other thing I could think that it could be is some sort of resonance or exhaust leak.

 

[lzaffuto]

Dropped the car off, of course someone didn't put the appointment I called in 2 weeks ago into the computer(amazing how often that happens isn't it?) and there is a week long lead time to be able to thoroughly check it out. They are going to replace the differential fluid in the meantime, but that is all they have time to do for now.

 

[GT Pony]

Dropped the car off, of course someone didn't put the appointment I called in 2 weeks ago into the computer(amazing how often that happens isn't it?) and there is a week long lead time to be able to thoroughly check it out. They are going to replace the differential fluid in the meantime, but that is all they have time to do for now.

That's a start. Ask them to pay close attention for any abnormal metal in the fluid they drain out, and also if the level was full like it should be.

 

[lzaffuto]

Fluid change made no difference... waste of $130. Now I have to find a dealership that will actually schedule me to look at the car and take it seriously. This makes two that I have been unimpressed by.

 

[magnus_1986]

Something similar happened to me in my Subaru Legacy, it was the wheel bearings.

 

[lzaffuto]

Update: Last Saturday I went out for a drive and the car started making a terrible grinding/scraping noise and vibration at low speeds in addition to the whine/hum at highway speeds. I parked it until I brought it in for my scheduled appointment last Tuesday. Just got an update from the dealership that there is definitely something wrong inside the differential and they are ordering parts and trying to get an ETA for me for when it will be fixed and call me tomorrow. He didn't tell me what they are ordering (it didn't sound like he knew much about it other than someone told him it was the differential) but I will see if I can talk to a technician when he calls me back for an update.

 

[ScottsGT]

Subscribing to this one. I'm hearing something too, but I think it my be tires I'm hearing.

 

[Bomorgan123]

Sorry to bump this, but did you ever figure out what was causing the trouble, OP?

 

[lzaffuto]

They rebuilt the differential... IIRC, they found some sort of ring that was installed improperly at the factory. However, when they gave the car back to me the grinding/scraping noise had stopped but the original humming noise was still there. Ford shrugged their shoulders and wasn't willing to do anymore on it so I sold the car before the warranty expired on it.

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