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  1. #1

    Default Clarification on gear oils

    Hello folks,

    I have specific and general questions about gear oils.

    Application is an '83 GT 5.0L 5-speed. I don't have my shop manuals handy, so what is the correct gear oil for the 7.5" axle with limited slip differential? What is the correct lubricant for a non-world class T-5?

    Kind of a general question here... application is 1968 F-250 360 NP435 4-speed and Dana 60 limited slip axle. I have read online about GL-4 and GL-5 gear oils. Is this a classification of gear oil like the API rating for engine oils? My understanding is that the NP435 4-speed would require a GL-4 gear oil (I believe 90w was originally called for) because this older transmission has materials in it that GL-5 does not sufficiently protect ("yellow metals" is a term I see frequently).

    Additionally, I don't think that an axle would be picky about GL-4 or GL-5 specification lubricant... would it? Seems like the ring and pinon gears won't care too much about what oil is in there, provided there IS oil of the correct weight.

    If someone could provide some clarification I would be greatly appreciative!

    Thanks guys,
    Michael

  2. #2

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    T-5 originally required Dexron II-D and that has been superseded by Dexron III (Dexron II is not longer made/discontinued)

    Dexron is an 'automatic transmission fluid'
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  3. #3

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    Thanks, FoxChassis! Appreciated as always

  4. #4

    Default

    I like Ford Type f if you can find it. It tends to shift smoother than dex, in my experience. out back 75W90 is fine daily, with maximum 4 oz of Ford fish oil (can buy this from any ford dealer). It doesn't care about GL4 or 5. The problem is when people use the wrong one of those in a transmission with brass or bronze parts.

  5. #5
    FEP Senior Member droopie85gt's Avatar
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    Default

    He said NON World Class T5.

    That's a different animal.

    50 weight gear oil. World class T5 take ATF.


    https://www.moderndriveline.com/md_f...shtml#02136499
    1985 GT, Sunroof, 5 Lug, Rear Discs, 01 Graphite Bullets, 88 forged piston shortblock, 2.02/1.60 Alum heads, Weiand Stealth, Holley C950 TBI, BBK Long tubes

  6. #6

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    Quote Originally Posted by droopie85gt View Post
    He said NON World Class T5.

    That's a different animal.

    50 weight gear oil. World class T5 take ATF.


    https://www.moderndriveline.com/md_f...shtml#02136499
    NO.

    ALL T-5 in Ford models take Dexron. ALL of them. NOT gear oil
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