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ATF in a muncie?

Discussion in 'The Hokey Ass Message Board' started by skwurl, Sep 1, 2008.

  1. skwurl
    Joined: Aug 25, 2008
    Posts: 1,619

    skwurl
    Member

    I had a discusion with this older guy who told me had converted his muncie so he could run ATF. ATF is thinner than gear oil obviously. could this be done and would it even be worth it?
     
  2. dana barlow
    Joined: May 30, 2006
    Posts: 1,962

    dana barlow
    Member
    from Miami Fla.

    no,viscaity is not there,oil for hard grear contect[standard tran.] must have thick to sofen the gear impack.......
    Very thin oil is used for drag racing ,were low HP dose not bang the gears,giving a small drop in drag,but not good for high HP big loads.
     
  3. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,132

    scottybaccus
    Member

    I did a lot of reading when shopping for my trans and never saw anything about ATF in a Muncie. I settled on a new M21 from Auto Gear Equipment. I am looking at the install sheet and it says:

    " We recommend filling your new transmission with a good quality SAE90 gear lubricant meeting API specifications GL4 or GL5 AND MT1. DO NOT USE GL5 lubricants without the MT1 label; the EP additives in unmodified GL5 lubricants have been found to damage the bronze used in bushings and synchronizer rings."
     
  4. The Shocker
    Joined: Dec 30, 2004
    Posts: 3,531

    The Shocker
    Member

    What would be the point on a street car or cruiser ? As you said its thinner and more prone to leak than the thicker 90 weight ...
     
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  5. skwurl
    Joined: Aug 25, 2008
    Posts: 1,619

    skwurl
    Member

    yea it sounded kinda out there to me. I'm running an m-21. i'm running sae 90. Thnks for the input.
     
  6. skwurl
    Joined: Aug 25, 2008
    Posts: 1,619

    skwurl
    Member

    I would be more worried about burning the thing up!
     
  7. 32v
    Joined: May 20, 2007
    Posts: 788

    32v
    Member
    from v.i.

    the getrag 5 and 6 speeds man. trans uses dextron 111 fluid same as atf about the same consistancy as 5-30 wt
     
  8. Bodacious
    Joined: Apr 4, 2008
    Posts: 286

    Bodacious
    Member

    There are plenty of manual transmissions around that do use ATF or other lighter lubricants. But generally for reasons already mentioned, and/or unless it's been modified to use a lighter oil, it's best to stick with a manufacturer's recommendation.
     
  9. propwash
    Joined: Jul 25, 2005
    Posts: 3,838

    propwash
    Member
    from Las Vegas

    I'd be inclined to think that unless the modifications include removing all bushings and putting EVERYTHING on HD roller bearings, ATF just wouldnt to the job at all. Not to mention the total loss of pressure cushion when the gears intersect with each other. I'm always amazed at the disinformation provided by folks that think that any modification used by racers (who spend a lot of time rebuilding after x number of races - so longevity is hardly ever an issue) must be a good modification for street use.

    "wake me up early, be good to mah dawgs, and teach my children to pray"

    dj
     
  10. Bodacious
    Joined: Apr 4, 2008
    Posts: 286

    Bodacious
    Member

    There are plenty of stock manual transmissions running around that have ATF factory installed. This is why I said in most cases, it's wise to stick with the factory type fill. HD OTR truck transmissions only use 50 weight oil. Believe it or not, high viscosity is not always the end-all of lube protection.
     
  11. BAD ROD
    Joined: Dec 16, 2004
    Posts: 1,413

    BAD ROD
    Member
    from Rescue, CA

    I use ATF in my T56 6-speed. I don't know anything about it, but I bet you could modify a muncie to run on ATF.

    Mike
     
  12. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,132

    scottybaccus
    Member

    Propwash is correct.

    ALL of the modern manual transmisions using ATF are using roller bearings. It won't work well in extended use in a bronze bushing transmission.
     
  13. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,305

    Flat Ernie
    Tech Editor

    This is an important tidbit - it's harder to find GL4 products as time passes. The GL5 stuff works great in rears, but older trannys will be damaged if they don't have the MT1...
     

  14. I'd be interested in what conversions he'd done.
    Other than draining the gear oil and pouring in ATF.

    I'll bet it was a secret and he wouldn't tell you.



    My favorite one from days gone by was the guy who'd put Zephyr gears in a 55 Chevy transmission.:confused:

    Or the guy who'd put an Olds crankshaft in a
    flathead block.
    that would've taken some serious engineering to say the least.
    And, best part was the guy doing the telling had a hard time drilling holes with a drill press....:D


    Micrometers hell!
    I gots me an aluminum yardstick....:D
     
  15. btmatt
    Joined: Nov 15, 2006
    Posts: 227

    btmatt
    Member

    Gear and bushing clearances are much "looser" than the newer transmissions. The older trannies need the thicker oil to absorb shock.
     
  16. 90 wt. was designed to absorb heat from normal running. All the older trans were sent out with this. I'm unaware of any reason to change this. My Tremec 3550 has a GM syncromesh oil that looks like 50 wt. It's still an older trans compared to any 6 speed. It's based on the Ford top loader 4 speed from the 60's. I wouldn't try anything lighter than that.
     
  17. draggin breath
    Joined: Feb 5, 2006
    Posts: 513

    draggin breath
    Member

    mopar A-833's left the factory with ATF.
     
  18. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,305

    Flat Ernie
    Tech Editor

    The conversion to ATF-type lubricants in the mid-80s had as much to do with shift feel as it did anything else. All else being equal, lighter gear oil shifts easier - hence early Ford recommendations of 90WT in winter & 140WT in summer.

    The NWC T5 originally called for 70-90WT gear oil, but all changed to ATF (even NWC) later...

    I'd be leery of using ATF in any older-style trannys...(but I do run it in NWC T5)
     
  19. 38fordcoupe
    Joined: Aug 24, 2004
    Posts: 83

    38fordcoupe
    Member

    Back in the mid to late 60's I knew a bunch of guys that ran ATF and a pint of STP in their "race only " 66 and 67 Nova's and Chevelles. It would warm up faster and shift nicer then 90wt. It was not recommended for a everday driver though. Don't remember anyone that "lunched" a tranny from using it.
     
  20. Ron
    Joined: Mar 3, 2001
    Posts: 1,168

    Ron
    Member

    A guy that used to be my neighbor worked at the trans plant for 30/40 years. I was telling him I had a Camaro with a t5 that blew up at 50k, that used ATF. He told they tried some t5's with gear oil instead of the ATF and he said the worked better with the heavier oil. He did not say what was better just that they did better.
     
  21. skwurl
    Joined: Aug 25, 2008
    Posts: 1,619

    skwurl
    Member


    <HR style="COLOR: #e5e5e5; BACKGROUND-COLOR: #e5e5e5" SIZE=1> <!-- / icon and title --><!-- message -->
    He seemed fairly knowledgeable. he is an inspector for car manufcturer's. He comes in and checks out things to determine if its driver error or a manufacturing defect. Basically can get your warranty voided for ya. He's supposedly an old hot rodder. I could'nt get past the "why would you do that thought" in my head to ask how he supposedley did it.
     
  22. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,305

    Flat Ernie
    Tech Editor

    Early T5 used bronze bushings - late T5 used bearings. Early (NWC) T5 used gear oil (70 wt). Late (WC) T5 use ATF. Factories later started recommending ATF for all T5...I use/recommend synthetic ATF in T5
     

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