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  1. #1
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    Diff Fluid and Friction Modifier

    I have a 2017 Daytona 392 Charger with the noisy diff issue. Bought her 3 weeks ago. 67k miles


    I have already changed the diff fluid 1 time and it got quieter for 1 week. Used Mobil 1 Synthetic 75W90 with friction modifier. 1000 miles since changed. Noise is back.


    I’m about to change it again. This time putting friction modifier in addition. How much should I add? 1/4, 1/2, Full bottle?


    Absolutely love the car. Hate low speed driving and turns. Sounds like a 50yr old farm truck
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    2017 392 Daytona Charger - Go Mango
    2017 Suburban



  2. #2
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    Mar 2021
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    Tylus,

    I am not familiar with friction modifiers, but I changed mine last week using Mopar 75W-140W
    took about 1.5q, I am amazed how quite it is now and how noisy it was.
    Likes Hemissary liked this post

  3. #3
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    Mar 2016
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    Friction modifier will not help with noise and perhaps make the clutches less effective. I think the experienced hands don't use it and put up with u-turn noise, and some add in one ounce increments to suit their tastes.

    When does the noise occur? In hard turns or @cruise?v Both.
    2013 Dodge Charger R/T Plus, Edelbrock E-Force 2300TVS 6.8 PSI, 450hp/459tq, Corsa CatBack, 3.06 Open Diff, Severe Duty Radiator, Dual Fans, OE Oil Cooler, Pursuit BR9 Brakes.



  4. #4
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    Sep 2006
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    It should be pointed out that the "noise" is not actually an issue / problem.

    As gapi states, friction modifier will not solve anything. Use a 75W140 gear lube...
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels


  5. #5
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    Sep 2006
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    Quote Originally Posted by BillB1 View Post
    Tylus,

    I am not familiar with friction modifiers, but I changed mine last week using Mopar 75W-140W
    took about 1.5q, I am amazed how quite it is now and how noisy it was.
    The modifier serves only one purpose; to minimize chatter from the two clutch assemblies when turning tightly at slow speeds. This is an NVH issue - not a performance / functionality issue. End-users get it in their head the the minor chattering they hear from time to time implies something is wrong...there isn't.
    Last edited by Hemissary; 04-06-2021 at 06:42 PM.

  6. #6
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    Dec 2016
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    Ft. Lauderdale, FL
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    Lol farm truck reference Diff Fluid and Friction Modifier


    Sent from my iPhone using Tapatalk
    '21 DD R/T White/Red/Blacktop, '19 Challenger Wide body Scat Pack B5; '19 Scat Pack F8 Green; '18 Audi SQ5 Daytona Grey; '18 Daytona 392; 16 Scat Pack Granite; '15 Durango R/T Blacktop; '14 Volvo S60R Rebel Blue; '12 Audi Q5; '10 Mustang; '08 BMW E90 M3; '07 BMW 335I Active Autowerks ...

  7. #7
    Join Date
    Jan 2015
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    Quote Originally Posted by BillB1 View Post
    Tylus,
    I am not familiar with friction modifiers, but I changed mine last week using Mopar 75W-140W
    took about 1.5q, I am amazed how quite it is now and how noisy it was.
    I used a blend. 1 qt of the 75W140 this time with 2oz of friction modifier and then topped it off with 75w90. Oil that I drained tonight was black. Had maybe 1,000 miles on it. I may not have flushed it out good enough last time.

    last fluid change was 75w90 only. It did quiet her down for about 1 week. I’m hoping the thicker fluid and FM helps out. Driving me nuts groaning.

    Quote Originally Posted by Hemissary View Post
    It should be pointed out that the "noise" is not actually an issue / problem.

    As gapi states, friction modifier will not solve anything. Use a 75W140 gear lube...
    It is not physically a “problem”. It is however a nuisance noise. For a nice car that shouldn’t sound so horrible. My 2012 Challenger with 3.90 gears never did this. Nor has ANY vehicle I’ve owned with lockers or limited slips/posi diffs. It is not normal and should not be considered NVH. It’s a design issue. You can read a 100 posts online about Dodge just replacing diffs for this noise. If it were just NVH Dodge wouldn’t do that.

    I wouldn’t put up with noise like this from my Daughters 2006 Mariner with 200k miles. Much less my relatively new mid-life crisis family car.

    I appreciate your concern for ruining the clutches. That’s good advice. I did use the 75w140 (mostly) this time.

  8. #8
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    Aug 2006
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    I do not have any experience with Chrysler anti-spin diffs but I do with eaton posi-tractions that were used in my 65 Chevelle and 69 SS396 Chevelle. Both had 12 bolt diffs with eaton posis. When my 65 got to about 80k miles, the posi unit started popping and snapping when the car was turning. It got really loud and annoying. Changing the fluid got rid of the noise. Back then (68) the posi fluid was only available at the dealer in qt cans. I never had any problems with the posi in about 100k miles that included lots of drag racing. Fast forward to my 2000 F150 with the Ford traction lock 9.75 rear. It started popping and snapping at about 80k miles only in turns. Replacing the fluid with Motorcraft 75w140 synthetic (only available at the dealer) and one bottle of friction modifier did not stop the noise. I found a tech bulletin on the subject where Ford recommended replacing the clutch pack and removing 0.010" of shims to reduce the preload on the clutch pack. I just added another bottle of Motorcraft friction modifier and didn't have any more chattering. That unit was still working fine at 170k miles. My current 2002 F150 with the 9.75" rear has a traction lock unit that is a little tight meaning that it locks up very quickly in turns but never makes any noise. 165k miles on it. I did change the fluid once when I had to replace an axle bearing and axle. I used Valvoline synthetic 75w140 and it claimed to be for traction lock rears so I did not add friction modifier. that may be why it locks up so quickly but there is no noise so I don't mess with it.

  9. #9
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    Mar 2016
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    Pearl Harbor eh? I'm not experienced with the 2015 & up Diffs' in these cars but if I could get it to Unitrax in Anaheim CA for a go through, I would and be done with it. Give them a call at least and describe it. He is great to speak with. You can ship it to them. Bench job turn around's are quick.

  10. #10
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    Apr 2018
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    I just changed mine a week ago or so with Amsoil Severe Gear 75w90 and a whole container of Amsoil Slip Lock. Opened the fill, drained the old fluid (it was black) and capped it when it was done, filled it up with the whole quart. Squeeze pack made it stupid easy. It was pretty cheap too, I think less than $30.

    If you haven't done it, I'd recommend it, it's VERY easy to do. Be warned though, gear oil is STANKY!
    2017 Pitch Black Charger Scat Pack 392
    20% tint, BT Matte Black Catch Can, LED interior lighting, ZL1 Rock Guards, K&N drop in filter, MaxBeam Smoked LED side markers, 20x9.5/20x11 HR5 Hell Raiser wheels w/ Conti DWS06 275/315 w/ 3mm spacer.

  11. #11
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    Yes stanky!!!!
    2018 R/T Scat Pack7.355 @ 96.07
    SOLD 07 Plum Daytona 12.854 @ 106.73 Stock Heads, Cam, Intake & Muffler
    7.50 with a ZERO! @ 94.94 mph on a 7.50 Dial In.

  12. #12
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    Yes stanky!!!!

  13. #13
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    Jan 2016
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    Sorta question regards to the rear diff. I never changed my rear diff (2016 ) until I changed it with my normal spring oil change. Basically 5 years.

    Didn't look bad, it looked like new motor oil. Light brown with very little to no sent to it.

    Never had any issues but I think it might be Transmission related. I still get really hard skips between first and second gear. Any way I can check to see if there is any updates...for the transmission?

    Owner of a 2020 Ram Laramie (leveled with 2" rc struts and 1" rear spacer on 33.5" toyo open country) , 16 Dodge Charger scat pack and my wife 21 Jeep Wrangler Unlimited Sahara (2.5" rc lift with 35" duratracs)

  14. #14
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    Apr 2018
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    If your rear diff gear oil didn't stink when you changed it, I'd be worried. It should stink like rotten butthole. I wouldn't be too worried about the color but the smell... I'll never forget that smell.

  15. #15
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    Sep 2006
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    The odor is sulphur; a significant component that's part of the extreme pressure additive used in hypoid-based gear oil (not the oil itself)...

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