Bad rear end gear oil experience.

Discussion in 'Mustang Chit Chat' started by Anti, Aug 9, 2019.

  1. Pentalab

    Pentalab forum member

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    I use Royal Purple 5W-30 HPS in my 2010 4.6 (with small Roush M90 blower). Between the synerlec and the elevated levels of ZDDP, I'm a happy camper. Runs smooth as a baby's bum.
     
    1950StangJump$ likes this.
  2. 08MustangDude

    08MustangDude forum member

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    Engine oil has nothing to do with hypoid gear oil...
     
  3. 1950StangJump$

    1950StangJump$ forum member

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    I think he was pointing out how the previous posts about all RP stuff being junk are inaccurate in his opinion.
     
  4. Pentalab

    Pentalab forum member

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    Precisely. I get it wholesale from a local buddy, who runs a marine repair shop....and also a mustang owner. 4.6 / 5.0 Engs stripped down after 100K miles look new, no wear. That's good enough for me. I don't lose any oil between changes.

    Use any eng oil you want.... just make sure it's 100% synthetic.
     
    Last edited: Aug 12, 2019
  5. WJBertrand

    WJBertrand forum member

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    I put RP 75w-140 and Ford’s recommended additive into my ‘13 GT’s differential. No chattering, whining or any other strange noises.


    Sent from my iPhone using Tapatalk Pro
     
  6. 08MustangDude

    08MustangDude forum member

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    I may drain it again and put 75W140 in mine, see what happens...
     
  7. travelers

    travelers Senior Member

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    That would be a good idea and some additive
     
  8. 08MustangDude

    08MustangDude forum member

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    I don't have an LSD, 7.5" open diff, no need for friction modifier. I do use that
    Synthetic Lucas oil stabilizer.
     
  9. eighty6gt

    eighty6gt forum member

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    Who is JimC?
     
  10. 08MustangDude

    08MustangDude forum member

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    He knows who he is... That's all that matters...
     
  11. RocketcarX

    RocketcarX 95% of my weight is fuel

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    Yes, lets ask the dope dealer if his shit is good.

    Take the time to google oil studies that include Royal Purple and you will see it consistently ranks towards the middle/bottom.
    I have never be able to run a diff fluid in a Ford with Trac-Lok and not need a friction modifier, I've probably done it 1000 times over the last 20 years.
     
    Badd GT likes this.
  12. 1950StangJump$

    1950StangJump$ forum member

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    LOL, the dope dealer comment, while making you feel clever, does not support your position.

    RP specifically advertises and states on its bottle that no additional FM is needed, and the guy I talked to had no motive to lie to me about whether additional FM would help.

    What else do you reasonably want? Could a major fluid provider be lying, despite the obvious legal risk? Sure. And the FM you have been using could actually be cow sperm, and the FM provider has ripped you off.

    And, perhaps you have added FM "1000" times. So what? I doubt you have added fluid 1000 times without FM and then experienced chatter that was remedied with the subsequent addition of FM. So, your hyperbole means nothing.

    PS I didn't change my gear oil 1000 times .... just once and no additional FM added. No chatter.
     
  13. RocketcarX

    RocketcarX 95% of my weight is fuel

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    Most synthetic gear oils have that "feature", nearly every time I've not used friction modifier the car came back with noise.
    Fords in particular are sensitive to this, especially the carbon disc'd trac-loks.
    Again I encourage you to do some real research instead of the anecdotal experience of serving 1 vehicle 1 time.
    If the discs in your car are worn out they would be less sensitive to the need for a friction modifier, so maybe that is a factor in your luck.
     
  14. 08MustangDude

    08MustangDude forum member

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    1950StangJump$:
    RP can say it has an additive, and that you don't need one, but that does
    not mean it has the FORD formulated additive; they are NOT the same.

    Look at ATF and how many formulations there are. Chrysler had to make
    their own +3, +4 because of how they shift their transmissions. I have
    seen plenty of, you can use Dexron with an additive, and it's the same.
    THAT is 100% false. Dexron or Mercon will destroy a Chrysler transmission
    since the Ultradive no matter what additive claims to turn it into ATF +3 or +4.

    So, RP puts their friction modifier in their gear oil, but that doesn't mean it
    is compatible with the Ford LSD. What they say is: It is developed with hypoid
    friction modifiers, which are highly recommended to use in clutch or cone type
    differentials. It is made to reduce operating temperature and lower the coefficient
    of friction, although there’s no necessary additional additive needed.

    They are saying, they claim it is not necessary for an additional additive, but are
    NOT saying DON'T USE another additive.

    Ford says: Ford Racing Friction Modifier is recommended for use in 1979 to 2014
    Mustangs and is compatible with other brands of gear oil. One bottle is required
    for rear ends equipped with Ford traction-lock units. They do not have an exception
    for RP's oil.

    If RP says you do not need to use Ford's Friction Modifier, then they should pay for
    any damages to the clutch pack because of it.
     
  15. eighty6gt

    eighty6gt forum member

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    why not just buy oil from ford - same stuff it came with, give or take, and relax.

    Or just grab a new corvette, 59995 including destination! What a buy.
     
    Kyle2115 likes this.
  16. WJBertrand

    WJBertrand forum member

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    You could do that but Ford even recommends/requires that you also use the additive with their own oil, so I'm not sure what that gets you. I've read that all 75w-140 synthetic final drive oils all contain limited slip differential additives, but that lighter weights, like 75w-90, may not. Perhaps that's some of the confusion?
     
  17. rocky61201

    rocky61201 forum member

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    Fuck Royal Purple. The detergents in their manual transmission fluid caused premature wear on my synchro blocker rings and many have experienced the same problem. Because of that bad experience I won't spend the extra money for their motor oil, gear oil, or any other product they make. And I give zero fucks about the testimonials from their representatives saying how great their stuff is. What I do give a fuck about is the testimonial from a guy who has rebuilt 100's of rear axles and not getting paid for his testimonial. I remember when Royal Purple first got big about 10 years ago. Horsepower TV did a test where they swapped out all fluids for Royal Purple and got like 12 extra horsepower. Probably $50 bucks extra for the Royal Purple brand for just 12 horsepower and then hundreds more spent in repairs 25k miles later.
     
    Last edited: Aug 15, 2019
  18. 1950StangJump$

    1950StangJump$ forum member

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    I get the hesitation. It's hard to differentiate the "internet knowledge" from the truth. I've also read that too much FM is also bad, so I would be very hesitant to add more to a fluid that reports to already have FM. Almost seems easier to use oil that you know does NOT have FM, and then add some.

    I just wrote Royal Purple again to see if they would put it in writing that it meets the requirements specific for my 2008 Ford Mustang GT, or if additional FM is needed. I realize that, even if they put it in writing, that won't be enough for some of you. But I'll post back what they say.

    Rocky -- I have heard many folks say that the RP for the manual trans was a problem for Ford syncros. My hunch would be that any issues that existed have long since been remedied by RP, but I don't know.

    Regardless, I wouldn't think the manual trans experience applied to all RP fluids, but I could see how you would boycott all of it based on your experience.
     
  19. 1950StangJump$

    1950StangJump$ forum member

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    Can anyone describe the noise (and when you'd hear it) that you would get if you don't have FM and needed it?

    I assumed I would know what "chatter" sounded like when I heard it, but let's be clear for the sake of this discussion.
     
  20. 1950StangJump$

    1950StangJump$ forum member

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    RP customer service answered already. They hedge just a little, but I think it is a good reply overall:



    "Thank you for contacting us. You should not need any additional friction modifier additive with our Royal Purple Max Gear 75W-140 (part #01301, quart bottle) in your 2008 Ford Mustang’s limited-slip differential.

    All of our Max Gear oils contain an appropriate dosage of the friction modifier additive that for most OEM and aftermarket performance type limited-slip differentials, no additional friction modifier additive is typically necessary. It is rare that any additional LSD-FM (limited-slip differential friction modifier) would be needed with our Max Gear oils. Please keep in mind that LSD-FM actually takes away LSD clutch grip, which allows the clutches to release more smoothly on tight turns. A large over dose of the LSD-FM additive is not desirable as it could reduce the effectiveness of your limited-slip differential unit's operation (possibly result with “one-wheel peel”).


    If a customer experiences a shudder on tight turns after doing a limited slip differential fluid change to our Max Gear oil, we will recommend taking the vehicle to a nearby empty parking lot and doing a couple of sessions of 10 slow and tight as possible figure 8s. The figure 8 procedure is often standard practice at car dealership service departments for limited-slip axle/differential oil changes. This works the fluid in between the clutches, and treats them due to the high differential in the wheel speeds. This normally will make the shudder in a limited slip differential that is in good mechanical condition go away.

    If you are still experiencing a shudder on tight turns after doing the sessions of figure 8s and some normal driving, then you may need to add a cap full or two of some additional friction modifier to stop the shudder. Don’t dump the whole bottle in though, as you already have what is considered a normal limited slip differential-friction modifier dose for most applications. Limited slip friction modifier can be purchased at your local Ford, GM, Jeep, Dodge or Chrysler dealer parts departments or bought from a local parts store, they are all basically the same stuff. Remember to repeat the figure 8s each time limited slip friction modifier is added, if you do need to add any additional friction modifier.

    Thank you for inquiring about Royal Purple, and have a great day!"
     
    Pentalab likes this.