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How's my gear oil choice?

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Kieran, Nov 10, 2015.

  1. Nov 10, 2015 at 8:06 PM
    #1
    Kieran

    Kieran [OP] Friendly Neighbourhood Canadian

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    So I got my tuck at 68,000km (42,200miles). I was told at the time the 64,000km (39,700miles) service had been done. I was desperate for a vehicle (after a total loss) so i got the truck on the dealers word. The dealer was a massive Toyota dealer near Toronto. Recently I was looking through the service history and noticed I couldn't find the the 64k service history. I contacted the dealer this week to enquire where that history was. He told me today it was just an oil change at 64k. Needless to say I am pissed I was lied to. But that is nether here nor there.

    So today I am buying a couple of gallons of gear oil to change my differentials, transmission and transfer case.
    I have looked through a bunch of threads (and service manual) and what oil is available on Amazon (its easy and I am hurting to get this done).
    It seems Redline MT-90 is the popular choice for the trans and transfer. As for the differentials it seems any 75w-90 is what people are using. The manual has 80W-90 as the oil to use but 75W-90 seems to be what people are using. For that Synthetic Lucas Oil 75W-90 is what I found.

    So with that long winded explanation. What are your thoughts on my oil choices? Anything I am missing?


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  2. Nov 10, 2015 at 10:53 PM
    #2
    landphil

    landphil Wishin' I was Fishin'

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    I'd run the 75w90 in the T-case too, rather than the MT90. It's a good choice for the Transmision though.
     
  3. Nov 10, 2015 at 11:07 PM
    #3
    Kieran

    Kieran [OP] Friendly Neighbourhood Canadian

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    Cool,
    Thanks for the info.
    What is the major difference between MT90 and 75W90... it is listed as 75W90 weight?
     
  4. Nov 11, 2015 at 7:10 AM
    #4
    obscurotron

    obscurotron Well-Known Member

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    Too many to list, and I've probably forgotten a bunch.
    The MT-90 (a 75w90 oil) is formulated for manual transmissions, and meets the GL-1, GL-3, and GL-4 specs, which is safe for certain non-steel components (i.e. brass). The RL 75w90 Gear Oil is rated for GL-5, GL-6, and several other specifications. Despite both being 75w90 (in this case), the viscosity of the two is different, and the MT-90 should have less (or no) sulphur.

    Many years ago some chemist figured out that if you added phosphorus and sulphur to gear oil, the oil would form a protective layer on steel under extreme heat and pressure (I think this is similar to the process for carburizing, but I'm not sure). When the contact surfaces mesh, the protective layer would absorb most of the wear, flake off, and then reform over and over again until there was no more additive package. When this layer forms on softer metals, like brass, it still flakes off, but it takes minute amounts of brass with it. That accelerates the wear.

    Since the viscosity and additive packages are different, The RL Gear Oil is also more slick. Synchromesh transmissions rely on some amount of friction, which typical differentials do not require.

    You could get away with running MT-90 in the 6 speed transmission and the transfer case (the trans wants GL-4, the t-case wants GL-4 *or* GL-5). The newer differentials call out 75w85, GL-5. There is no allowance for running a GL-4 oil in the differentials. You could, but you won't have as much wear protection over the long haul. The older differentials seem to be all over the place. Some call for 80w90, I've seen some that want 75w90, and then the newer ones mandate 75w85. I think the latter is junk, based on fuel efficiency standards. The next time around, I'm swapping in RL 75w90 in the front and rear.
     
    surforegon likes this.
  5. Nov 11, 2015 at 7:37 AM
    #5
    MariettaTaco

    MariettaTaco Well-Known Member

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    Let us know how the total job goes when you are finished. I've got to do the same thing.
     
  6. Nov 11, 2015 at 8:31 AM
    #6
    Kieran

    Kieran [OP] Friendly Neighbourhood Canadian

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    Thanks for the info. I was simplifying my comparison by weight without thinking about any chemical makeup.

    I ordered the following.
    2 gallons Lucas Oil Synthetic 75W-90.
    3 quarts Red Line MT-90
    1 pump thing.
    By my calculations that should allow me enough to flush some through the cases as well.
    Should take a couple of hours. My worry now is the weather here is getting cooler. I may just pay my dads mechanic some cash to use his lift/shop and do the work myself. I have been doing that for the 13 years I have owned a car. Comes in handy sometimes. We will see when the oil arrives how cold it is.

    Now today I tweak my clutch pedal to try and get the T/O betting to stop squeaking when in neutral.
     
  7. Nov 13, 2015 at 3:14 PM
    #7
    Kieran

    Kieran [OP] Friendly Neighbourhood Canadian

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    So I got everything done but the front diff. It was quite easy. Gave the bolts a little PB blaster love prior to attempting it. One thing I noticed was the inevitability of oil everywhere. The pump I got fit perfectly into a 3qt Rubbermaid juice mixing jug that I got. This allowed me to measure. Most spec measurements were fairly close. The transmission I was around 1/4qt shy of the measurement. It started to flow out despite my best efforts to put the correct amount of fluid. I let it drip a bit then put the cap on. I suspect there was a bit left that didn't drip out when I flushed it. All in all it was quite good.
    My calculations were good. It left me with 1/2qt of MT-90 and just over half a gallon of the Lucas synthetic. This was with flushing a bit out before I put the drain back on.

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    9b3167bd56c532a5438ba218060b1bd8_506493a5425a6728d8eee3df162830ce08270c98.jpg
     

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