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FJ40 overdrive unit

Discussion in '40- & 55-Series Tech' started by John Greene, Nov 14, 2007.

  1. John Greene

    John Greene New Member

    Messages:
    6
    I would drive my 1978 FJ40 more (don't have 40,00 miles on it yet) if it wasn't so wound up at 50 mph. I have thought about installing one of the "overdrive units" available on the aftermarket. Has anyone done this that could give me some results they realized? What does it do to rpm's at 50-55 mph. Has anyone checked miles per gallon on the road with one of these units?
  2. CruisinGA

    CruisinGA New Member

    Messages:
    6,152
    Location:
    Georgia Tech
    The overdrive units are not worth pursuing. Do a search for "fairey od" or some variation.

    You have three viable options- larger tires, smaller (numerical) ring and pinion ratio, or an overdrive transmission. In your case the H55 from Toyota would be the easiest to install. It is still available new from Toyota.

    Many people would be willing to trade their 3.70 ratio third members out of 79-83 FJ40's and all FJ60's for the desirable fine spline 4.11 ratio gears in your truck.
  3. CruisinGA

    CruisinGA New Member

    Messages:
    6,152
    Location:
    Georgia Tech
    3.70 gear ratio would drop your RPM's from about 2900 @ 65 mph to about 2600, assuming 31" tires.
  4. Fast Eddy

    Fast Eddy SILVER Star

    Messages:
    11,310
    Location:
    Morgan Hill, CA
    Stock sized tires? How about some rubber overdrive? 10% is easy.
  5. Jetboy

    Jetboy New Member

    Messages:
    1,118
    I'd vote for tires too. Something like a 33/9.5 can make a pretty significand difference in cruising ability. I'd probably go with a h41 and taller tires rather than an h55. That's just my opinion though, because I'd use the low gearing as much or more than the 5th gear. I'd guess either tranny is cheaper than an old bolt on over drive and probably more efficient. Less gears to spin before you get to the ground.

    THink about it this way; the slower you drive, the more time you get to enjoy driving a cruiser...
  6. DiHrdBowTi

    DiHrdBowTi Regular Member

    Messages:
    123
    Location:
    Reno
    I have the Ranger overdrive in front of my stock toy 4 speed but then I'm also running a 350. I like it.
  7. Advent

    Advent New Member

    Messages:
    548
    Location:
    Juneau, Ak; Fairbanks, AK
    I've actually got a Fairey overdrive that supposedly only has 15,000 miles on it that came out of a '78 (supposedly) FJ55 that I'm not using. Plans changed, but it appears to be fine.

    I think a lot of people's problem with them relates to not keeping them properly lubricated and tightened.

    They're sure as heck a lot cheaper than new gears or an H55F. For that matter, cheaper than a new set of tires. Not hard to install at all.
  8. brider

    brider New Member

    Messages:
    609
    I just installed a Fairey on my Pig that came off a '78 FJ40. Works great.

    Taller tires is easy, but affects your crawl ratio. So do 3.70 axles.
  9. Living in the Past

    Living in the Past SILVER Star

    Messages:
    8,443
    X2 you have to loss something to gain something. The H55F is a good tranny but longer than the H42 making a short rear drive line even shorter. With an overdrive you don't loss anything but your four speed now gives a overdrive plus eight forward gears in both high and low ranges.


    Jim
  10. My troopy has a fairey overdrive in it, and it really makes a difference in town. The original H41 (5:1 1st) is pretty low and even starting in second runs through the gears pretty fast when not in overdrive....

    The overdrive just makes it much more comfortable on the street...

    -H-
  11. 1962fj40

    1962fj40 Regular Member

    Messages:
    90
    Location:
    Phoenix, AZ
    Just caught this older post. Does anyone now where I may find a Fairey OD??


    Robert

  12. Degnol

    Degnol SILVER Star

    Messages:
    8,123
    Location:
    Kansastitty

    There is a Mudder that posted that he had eight Fairey OD units. I'm sorry that I don't remember who it was, but maybe they'll chime in.


    Ed
  13. grant5127

    grant5127 New Member

    Messages:
    5,021
    Location:
    Meridian,TEXAS
    Nice novlety....

    Has not been made for what, almost twenty years??

    Not aware of anyone providing product support for this toy...

    Save your money and purchase a Toyota five speed transmission...
  14. Combat Chuck

    Combat Chuck New Member

    Messages:
    2,936
    Location:
    Freensville
    H55 will mate up niecely to an F engie, and save you money on adapters. If you go aftermarket OD, or get a new tranny you'll have to move the T-case bracket back, and have the drive shafts adjusted.
  15. ranger

    ranger New Member

    Messages:
    1,147
    Location:
    Idaho
    I believe they still make them for Rovers under Superwinch. Not for TLC though.
    Finding parts is not easy as well.

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