SOLVED: New howling sound past 50mph

[edunn14]

In the last 250 miles or so my 2018 GT350 has developed a new noise - it sounds like air being blown over a bottle, and at times it is constant but the faster I go it starts to "pulsate" a bit for lack of a better term. It does this even when not in gear so I don't think it is engine/transmission related. When I take a longer, more sweeping turn it does get more pronounced.

I just got the car back three days ago from having the driver rear wheel bearing replaced; the shop specifically noted about a month ago it was the only wheel bearing that needed replacement after checking all 4.

I can't find anything here or elsewhere so far that covers this; I've seen some videos of a similar sound but no associated thread that comes to a conclusion on what the issue was. Some seem to say rear diff, others wheel bearings, others driveshaft (but I have no vibration issues).

Thanks in advance for thoughts/comments - this is my first RWD car and the exhaust/nature of this car leading to more inherent NVH is throwing off my ability to more accurately diagnose/describe.

Video below - it's faint b/c it's my cell phone but you can hear the "air over a bottle" noise at times.

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[Coosawjack]

Sounds like a lower pitched "Gear Whine" maybe.......since it seems to come and go at a specific speed??

 

[Arknsawchuck]

Id start by checking the diff. Change the fluid and see if anything odd drains out. Like lots of sparkles in the fluid. Since you already had the wheel bearing checked and one changed you'd think that's not it. But I have a deep distrust of repair shops especially dealership ones. Does it make any sound at parking lot speed?

 

[Champale]

I can't detect the noise in that video but to be clear, the noise started after they did the wheel bearing? I would imagine it's related to that repair.

 

[edunn14]

Changing that fluid may be a good idea. Car only has 30k miles but I'm the 4th owner I'm sure it's never been changed. I was under the impression it was a needless check unless I was tracking it but can't hurt now.

As far as I can tell, I hear no whine at parking lot speeds. The onset is VERY sudden speed-wise (meaning I don't hear anything at 40mph, but hear it by 50mph and above).

I took it on the highway yesterday (no crazy pulls or anything) and up to 80mph the sound was there but no drive-ability issues (steering wheel/body vibrations, power loss, changed handling, etc).

The noise started about a week before the repair. Honestly I thought maybe it was related to the wheel bearing and the work would eliminate it.

 

[Paddles]

What size/kind of tires do you have and how do they look? Some tires can wear funny sometimes and begin to howl at speed

 

[edunn14]

Tires look good, they only have about 6k on them. OEM Michelin pilot super sports in 295 front, 305 rear, 35/19 all around. And I don't spin them at all, I wait for grip before hitting the throttle. The car is a daily driver.

 

[526 HRSE]

That noise must be at the same pitch my wife speaks at, because i don't hear shit.

 

[edunn14]

Providing an update for future readers if they have this issue.

After some more driving and having some techs from local shops do some ride-alongs, the pretty unanimous opinion is that my rear diff is going. It is pretty consistent and more pronounced now, and sweeping turns in either direction exacerbate it pretty evenly. I guess I'll have to use that lifetime warranty from where I bought the car . . . we shall see how that goes.

I'm positive it wasn't anything I did that made it go; haven't touched the diff, 0 leaks, all maintenance kept up since I bought it, and 0 track time in my ownership. But the first 3 owners . . . who knows

When I get it in at the start of March we will see what they say.

 

[eisenhauer01]

Sounds like you got some solid info.
Keep us posted.

 

[icecreamtruckz]

Keep us posted. I got 33k miles on mine and just bought the fluids to do a rear end service. The carfax history seems to suggest the prior owner did service on time but who knows.

Curious what kind of financial damage a bad rear end would cause me.

 

[edunn14]

Not too keen on driving this thing another month without getting something done, and shops can't get me in for a "take the diff cover off and take a look" service until 2-3 weeks from now. I'm going to change the fluid out (OEM or Amsoil, haven't decided yet) this weekend and see what comes out/how things are after that. If I need to make a warranty claims I doubt a fluid change will make a difference to them.

 

[edunn14]

Changed the fluid out today. Pics below for reference. No signs of any leaks anywhere on the diff or axles that I could see, although you'll see there is SOME sort of fluid spot near the rear wheels. I started noticing that in the last month or two, but I figured it was just water/tire shine I was using when I detailed the car. Haven't washed or detailed it in about a month though.

Magnetic fill plug did not have anything concerning as far as what I see, pics below show it before and after cleaning. No large chunks. Feel free to chime in if you would be concerned by what is shown though.

Way less than 2qts drained out as you can see. I put 1qt of Amsoil Severe Gear 75w90 through it with the drain line still out to sort of "flush" anything that was left, then put 2qts of the same back in.

Results: mixed. The noise has definitely calmed down significantly, but it is still there at times. If you didn't know to listen for it, you may not notice it. I'm keeping my 3/3 appointment but I feel a lot better about driving it in the meantime.

PS: eff that retaining clip on the drain line . . .

 

[WItoTX]

That's how my drain plug looks every time. I wouldn't stress too much about it. IMO, it's your other wheel bearing, especially with it being more pronounced in the corners.

When my wheel bearings went bad, they had zero play. I just kept getting a suspension fault light and fault speed sensor error. Pulled the bearings, sure enough it all went away.

I can't hear anything in the video, but I can tell you mine has an ever so faint howl, that has been noticable since I put the rear seat delete in.

 

[eisenhauer01]

When you had the car up in the air, did you check to see if any of the wheels were "sloppy"? I had a noise like this on mine once and the rear axle nut on one side had loosened up.

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