Growling Differential/axle

[Charlesmax90]

Looking for some feedback if anyone has had a similar issue. 2018 premium ecoboost, 40k miles automatic limited slip differential door code GG which is 3.31 gear i believe. I've noticed a slight growling at slow speeds (under 10mph) when steering hard left or right (forward or reverse on gravel, grass or pavement). The sound dissapears after driving 5 mins. Ive tried coming back to a stop turning full lock left or right but cannot replicate the noise once the vehicle is warmed up. Before the sound goes away I can slightly feel a vibration in my driver seat and nothing in the steering wheel so im leaning more towards something on the rear of the vehicle. (This is a minimal sound and I have to focus to feel the vibration in the seat, it's almost insignificant but it's there.) Carfax shows this vehicle was in an accident previously but only the front bumper and hood were replaced. No mechanical damage reported.

The following items have been replaced/inspected in the past week. Front wheel bearings/tie rods ✅️ rear differential fluid replaced with (1.9qts of valvoline 75w-90 w/friction modifier filled to the bottom of the fill plug) 4️ new tires ✅️ (cv axles didn't feel like they had any slack)

The car drives flawlessly with a slight pull to the left (havent gotten an aligment yet but im certain nothing upfront is causing the growling noise). The driver rear tire had a very odd inner wear pattern but that could have been from a busted belt (the tires were old). Also the rear differential fluid was a lot darker than I would have liked to see but there was no sign of metal shavings or deposits in the oil.

I drive the car an hr back and forth to work and the growling noise doesn't seem to be getting worse or better in the 1800 miles. Also the issue doesn't seem to affect the fuel mileage. Calculating 28.9mpg on paper. Which matches my previous 2018 ecoboost.

I'm almost certain the issue is coming from the rear end. Someone suggested rear cv axles but in my experience the sound would not go away after a few minutes of driving and should gradually get worse over time. I wish I was wrong but I'm leaning towards something with the limited slip package rear differential. The abnormally dark color of the rear diff fluid has me concerned, although the unaffected fuel mileage seems to say it's not the ring/pinion gears. I plan to drop the rear differential oil again this week after putting another couple hundred miles. Experienced input would be appreciated. I'm not a fan of throwing parts at something to solve a problem.

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[Sparky1337]

If you didn’t have anything weird come out with the fluid I would suspect a wheel bearing.

 

[Skye]

Being unable to turn, It might not have the same effect, but I wonder if any tells would present at a shop. While the car is on a lift, the wheels free, and the drivetrain slowly (and safely) engaged, have a tech listening around and underneath the car. Just creeping really. Before or after, all four wheels could be turned and handled, to see if anything comes about.

You're looking forward to an alignment. Maybe the alignment shop could do before checking settings and making any adjustments.

 

[Mach VII]

Ecoboost came with 3.31 Trac-loc unless optioned with Performance Pack then it got 3.55 Torsen. 3.73's were never offered so it's weird you would have code BB on the door jamb sticker...

 

[308 Cal. Bullitt]

Could be a Tracloc issue.

Let the car sitting overnite, so it will replicate the noise in the morning.
Before driving, aim some serious heat at the center portion of the IRS to raise the temp measurably.
(e.g. a torpedo heater/small electrical heater that has fan to saturate the center section w/heat).

Then test drive.

Yet... If it's doing it on grass as you said, it's likely not the Tracloc, but who knows.

5 minutes (& it's gone) is hardly enough time to build significant heat into any ring & pinion, w/o a very significant load. Wonder if the interal plate load on clutch pack is somehow a factor??

I doubt the heat will show ya anything, but it's still better than parts tossing yet again just yet.

 

[Jerryinpa]

Hi,
There's post about the rear hubs n bearing failures on this site. Also the axle nut loosen up which can cause the hub bearing to fail.
Thanks, Jerry

 

[Charlesmax90]

If you didn’t have anything weird come out with the fluid I would suspect a wheel bearing.

A wheel bearing that only growls at low speeds and stops when it's warm? I guess anything is possible, but I've replaced many on numerous vehicles and never had one get silent at higher speeds after warming up.

 

[Charlesmax90]

Hi,
There's post about the rear hubs n bearing failures on this site. Also the axle nut loosen up which can cause the hub bearing to fail.
Thanks, Jerry

News to me, thanks!

 

[Charlesmax90]

Ecoboost came with 3.31 Trac-loc unless optioned with Performance Pack then it got 3.55 Torsen. 3.73's were never offered so it's weird you would have code BB on the door jamb sticker...

I'm an idiot, was looking at the wrong code. "BBKK" at the far end. Axle code was right in front of me "GG" = 3.31 I'll correct the original post, thanks!

 

[Charlesmax90]

Could be a Tracloc issue.

Let the car sitting overnite, so it will replicate the noise in the morning.
Before driving, aim some serious heat at the center portion of the IRS to raise the temp measurably.
(e.g. a torpedo heater/small electrical heater that has fan to saturate the center section w/heat).

Then test drive.

Yet... If it's doing it on grass as you said, it's likely not the Tracloc, but who knows.

5 minutes (& it's gone) is hardly enough time to build significant heat into any ring & pinion, w/o a very significant load. Wonder if the interal plate load on clutch pack is somehow a factor??

I doubt the heat will show ya anything, but it's still better than parts tossing yet again just yet.

Not a bad idea. Also, if the noise is till there it would redirect my attention from the differential and lean more toward cv joint or bearing.

 

[WD Pro]

In my experience the Trac loc needs friction modifier.

I know you said your oil had it in, but if it's not as good, or dosed to the same extent as what ford specify, I would try that first

Dose it up, take it for a drive, do some slow tight figure of 8's, then see what it's like the following day

WD

 

[Sparky1337]

A wheel bearing that only growls at low speeds and stops when it's warm? I guess anything is possible, but I've replaced many on numerous vehicles and never had one get silent at higher speeds after warming up.

I’ve had wheel bearings do crazy stuff. But it’s also easier to check/fix over a rear diff.

 

[Racer5973]

Looking for some feedback if anyone has had a similar issue. 2018 premium ecoboost, 40k miles automatic limited slip differential door code GG which is 3.31 gear i believe. I've noticed a slight growling at slow speeds (under 10mph) when steering hard left or right (forward or reverse on gravel, grass or pavement). The sound dissapears after driving 5 mins. Ive tried coming back to a stop turning full lock left or right but cannot replicate the noise once the vehicle is warmed up. Before the sound goes away I can slightly feel a vibration in my driver seat and nothing in the steering wheel so im leaning more towards something on the rear of the vehicle. (This is a minimal sound and I have to focus to feel the vibration in the seat, it's almost insignificant but it's there.) Carfax shows this vehicle was in an accident previously but only the front bumper and hood were replaced. No mechanical damage reported.

The following items have been replaced/inspected in the past week. Front wheel bearings/tie rods ✅️ rear differential fluid replaced with (1.9qts of valvoline 75w-90 w/friction modifier filled to the bottom of the fill plug) 4️ new tires ✅️ (cv axles didn't feel like they had any slack)

The car drives flawlessly with a slight pull to the left (havent gotten an aligment yet but im certain nothing upfront is causing the growling noise). The driver rear tire had a very odd inner wear pattern but that could have been from a busted belt (the tires were old). Also the rear differential fluid was a lot darker than I would have liked to see but there was no sign of metal shavings or deposits in the oil.

I drive the car an hr back and forth to work and the growling noise doesn't seem to be getting worse or better in the 1800 miles. Also the issue doesn't seem to affect the fuel mileage. Calculating 28.9mpg on paper. Which matches my previous 2018 ecoboost.

I'm almost certain the issue is coming from the rear end. Someone suggested rear cv axles but in my experience the sound would not go away after a few minutes of driving and should gradually get worse over time. I wish I was wrong but I'm leaning towards something with the limited slip package rear differential. The abnormally dark color of the rear diff fluid has me concerned, although the unaffected fuel mileage seems to say it's not the ring/pinion gears. I plan to drop the rear differential oil again this week after putting another couple hundred miles. Experienced input would be appreciated. I'm not a fan of throwing parts at something to solve a problem.

Sounds like a hub bearing just starting to go bad.

 

[PSI]

I’ll second the suggestion from WD Pro that you need friction modifier. My GT has the 3.15 limited slip, and after changing the fluid with the exact same Valvoline 75w90 for limited slip that you used, my diff would groan/rumble for the first few minutes on tight turns. Adding ford’s friction modifier fixed it.

 

[Charlesmax90]

In my experience the Trac loc needs friction modifier.

I know you said your oil had it in, but if it's not as good, or dosed to the same extent as what ford specify, I would try that first

Dose it up, take it for a drive, do some slow tight figure of 8's, then see what it's like the following day

WD

I've thought about this, I figured a week's worth of driving +/- 500 miles with the new diff fluid (which comes with friction modifier as you said). Would slowly work it's magic (assuming the diff is my issue) but it hasn't.

Keep in mind the growling noise was the same prior to replacing the diff fluid.

Also I'm a little conflicted on specific fill capacity for the diff. I found this chart stating 2018 requires a different amount of frictoin modifier than the 2015-2017 models which seems odd.

Doing the math for the recommended 1.6 qts oil plus the 3.28oz's of Friction modifier would total just over 1.7 qts of rear diff fluid. At what point are the tenths of a quart irrelevant? I went old school method and filled to the bottom of fill plug which is 1.9qts.

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