Unexpected Rear Diff Noise After Fluid Change (max tow with LSD)

[sdk131]

Well....that was unexpected. I changed the rear diff fluid in my 2021 Sport S with max tow option. Having the track lock LSD I knew that the fluid required a friction modifier/additive. I read countless threads where people said "as long as you use something like Valvoline Synthetic 75w90 that already has the modifier in it you are fine". Low and behold a few miles up the road I stop at a sign and make a slow right turn only to hear a brand new noise coming from the rear of the vehicle. Its more of a deep/soft "growl" or "vrrwwrrr....vvrrrwwww" as I turn and it immediately goes away when I straighten out. I already ordered a 4oz bottle of the mopar friction modifier and will add some.....but this was very unexpected. I will post back after adding it, but I wanted to post here incase anyone else finds themselves in this unexpected position.

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[Tommyd]

Weird! Following I’d like to know the result.

 

[Hootbro]

I have always disregarded the gear oils labeled as having the friction modifier in them and added the modifier anyways as you can probably find Jimmy Hoffa's body quicker than the gear oil manufacturers specs of what exact additive composition they have and at what concentration. *

*Ignore the run on sentence.

 

[sdk131]

Reporting back - I added about 3oz of the mopar friction modifier, drove around in tight circles for a minute or so and the noise went away (I'm assuming once the modifier was thoroughly mixed in and reached all the nooks and crannies of the LSD). I don't claim to be a mechanic or lubrication engineer....so make your own judgements on what you do if servicing the Dana 44 axle with the LSD versus the locker.

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