1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

3 speed to 4 speed

Discussion in '40- & 55-Series Tech' started by fj40mayo, Aug 19, 2003.

  1. fj40mayo

    fj40mayo

    Messages:
    402
    Likes Received:
    0
    Joined:
    Aug 11, 2003
    Location:
    Fort Worth
    I have a '73 fj40 w/ a 350 and a 3 speed transmission and transfer. If I go to a '79 4 speed and transfer, will it bolt right with the same adapters that I have now? I have a gm bellhousing with a spacer between it and the transmission and a crossmember bolted to the transfer. Wouldn't the higher gear of the 4 speed transfer make the 1:1 4th gear better on the road than my 3 speed? Please help
     
  2. Rice

    Rice SILVER Star

    Messages:
    3,277
    Media:
    10
    Likes Received:
    2,578
    Joined:
    May 2, 2003
    Location:
    GSO NC
    Both 3 and 4 speeds have a 1:1 final gear as is the TC. There will be no difference for on road travel. All you will have is closer spacing between each gear. For better road travel your only choices are bigger tires, changing the rear ends, or putting in an overdrive unit (which could include a 5 speed such as the NV 4500). If you opt. to get rid of the 4 speed and TC drop me a note ... I can use them both.

    Good luck.
     
  3. woody

    woody Internet Fireman Staff Member

    Messages:
    10,336
    Media:
    303
    Likes Received:
    1,099
    Joined:
    Jan 15, 2002
    Location:
    Toquerville UT
    it's a different adapter completely, plus you'll need driveshaft length changes.

    the 4-speed t-case is 1:1, same as the 1:1 ratio of the 3-speed t-case. top gear in both trannies is 1:1. You'll notice absolutely zero different at road speeds, other than the slightly quieter gears in the trans/t-case.

    In town, the 4-speed is nicer shifting and gives you that "middle 30mph gear" that the you are missing now.

    If your focus is offroadability, then swap in the SM465. If it's streetability, the Toy 4-speed is great. See http://www.advanceadapters.com for options on bellhousings.
     
  4. 72cruiser

    72cruiser

    Messages:
    2,709
    Likes Received:
    0
    Joined:
    Dec 29, 2002
    Location:
    nashville, tn
    you're missing the best part about the 4spd:

    SYNCHROs!!!! you'll actually be able to shift from 2nd down into 1st without stopping.

    also, it (outside of the adapter) is one of the cheapest trannies that you can swap for the 3spd.

    i was going to do the same swap, but now that my 40 is out of commission for a while, i'm probably goin to go nv4500 or try and find/figure out how to put in a h55.

    jonathan
    jmalphr@clemson.edu