Growling Differential/axle

[Charlesmax90]

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.

Thanks! Do you remember the exact amount of fluid you ran by chance? I'm right at 1.9qts to the bottom of the fill plug. Tried to go off of this chart but I don't see how .2 qts could cause any significant issues.

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[PSI]

Thanks! Do you remember the exact amount of fluid you ran by chance? I'm right at 1.9qts to the bottom of the fill plug. Tried to go off of this chart but I don't see how .2 qts could cause any significant issues.

I filled mine to a few mm below the fill plug and topped it up with FM. I didn’t use the whole tube of FM to do it but it was enough to shut it up.
I’ve read somewhere that proper fill level for these cars is 8 or 9mm below the plug.

 

[WD Pro]

I filled mine to a few mm below the fill plug and topped it up with FM. I didn’t use the whole tube of FM to do it but it was enough to shut it up.
I’ve read somewhere that proper fill level for these cars is 8 or 9mm below the plug.

'Within 9mm'

The smell of Fords friction modifier is like no other ...

WD

 

[PSI]

'Within 9mm'

The smell of Fords friction modifier is like no other ...

WD

Ever smell ACDelco supercharger oil after it’s been in service for a while?

 

[Sparky1337]

Ever smell ACDelco supercharger oil after it’s been in service for a while?

Them and TRD superchargers. I swear they made it out of whale oil. I did not like changing those one bit.

 

[Charlesmax90]

I filled mine to a few mm below the fill plug and topped it up with FM. I didn’t use the whole tube of FM to do it but it was enough to shut it up.
I’ve read somewhere that proper fill level for these cars is 8 or 9mm below the plug.

So you had the specific growling noise?

 

[PSI]

So you had the specific growling noise?

Yes, it was a groaning/growling noise at low speeds during tight turns such as backing out of my driveway, and only when the diff was cold. Ford LS additive made it stop, since in my case it was the sound of the clutch packs in the diff chattering that created the sound.
Not saying for sure it’s your issue but it’s a relatively cheap and simple potential fix that I’d look into before digging deeper.

 

[WD Pro]

Yes, it was a groaning/growling noise at low speeds during tight turns such as backing out of my driveway, and only when the diff was cold. Ford LS additive made it stop, since in my case it was the sound of the clutch packs in the diff chattering that created the sound.
Not saying for sure it’s your issue but it’s a relatively cheap and simple potential fix that I’d look into before digging deeper.

OP = You can sign my name on this exact same comment too, hence my first post in this thread

WD

 

[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

This is the next plan on my days off. Will update with results.

 

[Charlesmax90]

Dropped diff fluid again (it was clean). Had put about 500 miles on that fluid. Replaced with the same easy fill amsoil 75w-90 1.6qts (which contains friction modifier) but this time I added the 3.25 oz's. of Ford friction modifier.

This immediatly resolved the growling noise. I have put around 400 miles since and am confident there are no other issues. I apprciate the input. Hope this saves someone some time and money in the future.

 

[WD Pro]

Dropped diff fluid again (it was clean). Had put about 500 miles on that fluid. Replaced with the same easy fill amsoil 75w-90 1.6qts (which contains friction modifier) but this time I added the 3.25 oz's. of Ford friction modifier.

This immediatly resolved the growling noise. I have put around 400 miles since and am confident there are no other issues. I apprciate the input. Hope this saves someone some time and money in the future.

Good stuff, and I’m really glad you didn’t go down the ‘replace anything mechanical that rotates’ route …

WD

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