Changing final gear ratio
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Northstar Engines and System Technical Discussion Discussion, Changing final gear ratio in Cadillac Engine Technical Discussion; I apologize if this is in the wrong section - but I couldn't find any tranny-specific one... Anywho, how much ...
  1. #1
    eldorado1 is offline Cadillac Owners Connoisseur
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    Changing final gear ratio

    I apologize if this is in the wrong section - but I couldn't find any tranny-specific one... Anywho, how much work is it to change the gears from a 3.11 tranny to 3.73 gears?

    4t80e sorry..

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    BeelzeBob's Avatar
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    Re: Changing final gear ratio

    Quote Originally Posted by eldorado1
    I apologize if this is in the wrong section - but I couldn't find any tranny-specific one... Anywho, how much work is it to change the gears from a 3.11 tranny to 3.73 gears?

    4t80e sorry..
    It isn't the simplest nor easiest job but it is possible to remove the complete final drive assembly from the trans while the trans is in the car. The tail housing of the trans comes off after removing the wheel/tire, knuckle, drive axle, etc... then the final drive can be removed and replaced.

    If you replace the existing final drive with a 3.71 ratio the PCM cal that you have will not recognize this and will set some codes as it will think the trans is incorrect.....

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    I'm right in the middle of the swap. How in the **** do I remove the HUGE snap ring holding in the large gear? The one that's 8" in diameter, and 1/4" thick!?! I assume I need to compress it somehow to remove it from the grooev, but with what!?!

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    Nevermind, figured it out. What a pain that stupid snap ring was...

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    sts15l7 is offline Cadillac Owners Fanatic
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    Re: Changing final gear ratio

    damn. that seems like a hardass job eldorado1, to be doing urself at least.

    good luck, and be careful!

  7. #6
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    Naw, it's not so bad. Sucks to have a time restraint though (gotta be done by monday)

    Ran into a couple problems, but when in doubt, use a BFH.

  8. #7
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    w00t! No leaks, and it runs pretty good! All the cars should have 3.71 gears

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    Hason560 is offline Cadillac Owners Member
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    Re: Changing final gear ratio

    what about the codes? did you get any? i know you are into something very custom so i have no idea if you even useing the stock computer.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    Quote Originally Posted by Hason560
    what about the codes? did you get any? i know you are into something very custom so i have no idea if you even useing the stock computer.
    hehe nope - my computer thinks I'm running a manual

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    Re: Changing final gear ratio

    ...thinks you're running a manual? Aren't shifts controlled by the PCM in these cars?

  12. #11
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    Quote Originally Posted by davesdeville
    ...thinks you're running a manual? Aren't shifts controlled by the PCM in these cars?
    Yes - I built my own f1-style-paddle-shifting TCM to control the transmission.

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    Re: Changing final gear ratio

    holy smokes, that sounds cool! How did you do that? Show it off by posting some pictures.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Changing final gear ratio

    Quote Originally Posted by mtflight
    holy smokes, that sounds cool! How did you do that? Show it off by posting some pictures.
    How did I do it? I'm an EE, I build electronic gadgets

    It's not much to look at...... I'll be selling these on ebay and elsewhere if you're interested.......
    Attached Images

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    mtflight's Avatar
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    Thumbs up Re: Changing final gear ratio

    Very cool... all you need now is a racing seat with lateral support, and a helmet!

  16. #15
    duecentoi is offline Cadillac Owners Member
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    Re: Changing final gear ratio

    How do you get the PCM to still control line TV (for lack of a better term) pressure when taking shift control away from it? It will set a code if it isn't in the gear the PCM wants, after all. How much do you want for the paddle shift set up? Email me at flatboy@comcast.net, if you would.

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