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700R4 or 4L60????

Discussion in 'The Garage' started by desertrat, Sep 13, 2003.

  1. desertrat

    desertrat Newbie

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    Does anybody know how to tell the difference between a 700R4 and a 4L60? I have a 1991 with a 350/5.7 and RPO code MD8 for the transmission. Everything I can find on it, lists it as 700R4/4L60 which means that is could be either I guess. Did GM start using the 4L60 (not 4L60E) half way through the year?
    I'm asking because as I understand the 700R4 uses a mechanical Speedo adjustment (gears in the transfer case), and the 4L60 does it all through the VSS. I want to get my speedo functioning right again after going to 33s over the stock 31s. Should I just wait and put taller gears in it? RPO code shows I have 3.43. Will 3.73 be enough or should I go for 4.10? It does more time pulling boats and car trailers than off road these days.
    I am not a mechanic, and just learn as I do things, so opening something up that I haven't done before makes me a little leary. I don't want to screw it up the first time, and watch my wallet spring a leak to fix my mistake.

    Desertrat
    "being drowned in NC"
     
  2. sapper

    sapper 1/2 ton status GMOTM Winner

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    yours should be electric, i believe that was only change, where in NC are you?
     
  3. HarryH3

    HarryH3 1 ton status Author

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    The 700R4 and the 4L60 are the same transmission, only the name was changed to protect the guilty. /forums/images/graemlins/wink.gif The 4L60E is the electronically controlled version that has a lot of internal differences.

    However, that's a moot point unless you have a 2WD truck. On 4WD's, the speedo feed comes off of the transfer case. If it came off of the transmission, it would be WAY off when in low range. /forums/images/graemlins/shocked.gif Your '91 uses an electronic signal to drive the speedometer. Someone makes a speed ratio adapter (perhaps it's from Superlift?) that will let you alter the pusles between the VSS and the speedometer to trick the speedo into reading correctly. The only bad news is that is costs around $100. /forums/images/graemlins/eek.gif
     
  4. desertrat

    desertrat Newbie

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    I'm at the home of the Airborne in NC.

    Yes, the cable comes from the transfer case, and $100 was about what I was expecting. The only things I have seen so far to "trick" the VSS was for 92-94, not 91 and older. I know they changed a lot when they changed the body style, so I didn't think it would work (doesn't the 92 have a 4L60E?)

    DesertRat
    "keeping my head above the waterline in NC" /forums/images/graemlins/k5.gif /forums/images/graemlins/smile.gif
     
  5. SF87K5

    SF87K5 1/2 ton status

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    [ QUOTE ]
    doesn't the 92 have a 4L60E?

    [/ QUOTE ]
    Yes it does.

    I am at Ft Bragg also shoot me a pm if you want to get together for any work on your rig ok. /forums/images/graemlins/thumb.gif
     

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