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Transmission Speedometer gear: can I change it?

Discussion in 'The Garage' started by Ddragggon, May 8, 2002.

  1. Ddragggon

    Ddragggon 1/2 ton status

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    ok, my 77 C20 has a Turbo 400 behind a 454... the original 400 I had blew its reverse out. I got a `new' turbo 400, and put it in, but the rear end on the donor truck was a 3.73, whereas my current rear end is a 3.08. is it possible for me to just pull the speedo gear out of the side, and drop in the speedo gear from the other transmission? or is there more to it then that? I figgure I ought to ask before I inadvertantly destroy a transmission that's currently working fine...

    thankyou in advance,

    -Rich
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If I am not mistaken you can change the gear on the output shaft of the tranny but you will have to pull the tail housing off to do this. Now I am assuming you are talking about a 2WD vehicle since the 4WD speedo gears are in the transfer case and not the tranny.
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    For a 2WD TH-400 tranny you won't have to pull the tailshaft off.
    It is just as easy as disconnecting the cable and then unscrewing the cover plate that holds the speedo gear.

    <a target="_blank" href=http://coloradok5.com/gallery/albuo19/abw?full=1>Look at this picture... Part #5 "on some models" </a>

    I've had a hard time finding other gears to correct for rearend gearswaps... I've found the gears for 4 speed trannys but none for autos.
    IF your asking if you could swapt those speedo gears from one 2wd 400 to another 2wd 400 tranny then i'm pretty sure the answer is yes. /forums/images/icons/wink.gif
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Ryan, he needs to change the drive gear, not the driven gear that comes out the side. His driven gear is already the correct one for his vehicle but the tranny was swapped and it has a different drive gear than his original. In this case he will need to remove the tail housing in order to replace the gear with the correct drive gear.
     
  5. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Ahhhhh! I gotcha now! /forums/images/icons/wink.gif

    So do you have to use a puller to get the drive gear off the tailshaft?
    How would you go about removing that gear?
     

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