Saginaw 4-speed rebuild help
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Thread: Saginaw 4-speed rebuild help

  1. #1
    Administrator mt94ss's Avatar
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    Saginaw 4-speed rebuild help

    Anyone have any tips on rebuilding a mid '70s GM 4-speed? I have one and want to put it in my '55 but want to go through it first. Kit's appear to be real cheap.

    Are there any parts that should be replaced regardless? It looks like the input shaft is one of those. Are there any resources (books) that I can follow to do it right?

    Thanks in advance,

    Mike
    Liberty, In God We Trust, E PLURIBUS UNUM

    Watch my engine => http://www.youtube.com/watch?v=HDMbG7mMwW4
    My GMC http://www.c10trucks.com/forums/showthread.php?t=91

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  3. #2
    Senior Member Marks63PontiacGasser's Avatar
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    Boy, it's been a long time since I thought about the saginaws. One thing I remember is replacing the front wave spring washer (???? can't remember the actual name of it) with a torrington bearing. Some thing about the washer breaking and causing too much play??? One other thing that I was always going to do on the 4 speed Saginaws was, find an OD unit off of the 3 speeds and put it on the 4 speed to make a 4 speed overdrive. It's a bolt on addition but there was something about an actuation pin or something that had to be modded or?? I'm sorry for the lack of info. It has been 35 years since I thought about this. There should be info out there on GM boards etc. I remember them saying that the addiditon of the torrington bearing increased the strength of the Saginaws a lot. It was a major weakness. I hope the info helps and you can figure out what to do with. Mark L
    It's not a period gasser but it is what I would have built had I been of age to back then.

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  4. #3
    Administrator 1946Austin's Avatar
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    From what I've always read the Saginaws were a pretty weak trans, basically a 3 spd with one more gear. Not ssure I'd put one behind a engine with any power. Had one in my '67 Chevelle and after putting in a new clutch, the first burnout I did imploded it!

  5. #4
    Administrator mt94ss's Avatar
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    Oh great! Maybe I'll stick with the 700r4 until I can afford a TKO 500 or T56. The last thing I want to do is put it together and break it on the first run... I guess I need to do more research.

    Balloon deflated...
    Liberty, In God We Trust, E PLURIBUS UNUM

    Watch my engine => http://www.youtube.com/watch?v=HDMbG7mMwW4
    My GMC http://www.c10trucks.com/forums/showthread.php?t=91

  6. #5
    Senior Member Str8axle's Avatar
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    Sell the Sag and buy a Muncie.
    Ray

    All my life I've been told I'm a "Bad Influence"

  7. #6
    Administrator 1946Austin's Avatar
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    Yes, a Muncie M21 or a very strong M22, but steer clear of the M20, it's stronger than a Saginaw, but not by much. A Super T10 would be a good choice too.
    Last edited by 1946Austin; 06-23-2011 at 11:41 PM.

  8. #7
    Administrator mt94ss's Avatar
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    Why not an M-20? Isn't it stronger than a T-10? Here's a craigslist for an M20 wide ratio. http://portland.craigslist.org/wsc/pts/2446771550.html

    I thought that M20s were wide ratio, M21s were close ratio, and M22s had straighter cut gears for more torque. It seems like a decent deal for a good trans. I did some research online and couldn't find any structural differences between an M20 and M21 other that wide and close ratio. Is there a torque rating for what these trannys should take?

    Mike
    Liberty, In God We Trust, E PLURIBUS UNUM

    Watch my engine => http://www.youtube.com/watch?v=HDMbG7mMwW4
    My GMC http://www.c10trucks.com/forums/showthread.php?t=91

  9. #8
    Administrator 1946Austin's Avatar
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    Sorry, the M20 is the equal to the M21 in strength, I just don't care for the wide ratio.
    Last edited by 1946Austin; 06-23-2011 at 11:46 PM.

  10. #9
    Senior Member Str8axle's Avatar
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    When picking a M20, try to get one with a 1" counter shaft. The early 7/8" counter shaft trans are the weakest ones. But if the price is right, it'll suffice till you can score a better one. Still better than a Sag or T10 in my opinion.
    Ray

    All my life I've been told I'm a "Bad Influence"

  11. #10
    Administrator mt94ss's Avatar
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    After doing a bunch of reading about Muncies and decided on a M20. I found that the close ratio works best with 4:56 or lower gears. I have 3.73s. The lower 1st gear 2.56 instead of 2.20 makes for quicker starts with the 3.73 gears.

    I picked up a M20 - wide ratio from '64-'65 - 7/8" shaft. It came with a Competition Plus shifter and the price was right.

    The guys at Garage Motorsports said that this will handle the 400 HP no problem. I got the parts to rebuild it and will decide when I'm in it if I'm going to change it to a 1" shaft. They even got me updated synchros (late style) and the collars that go over the hubs that keep the tranny from popping out of gear when decellerating.

    I will go through the shifter also.

    Can't wait to get into it.

    Mike
    Liberty, In God We Trust, E PLURIBUS UNUM

    Watch my engine => http://www.youtube.com/watch?v=HDMbG7mMwW4
    My GMC http://www.c10trucks.com/forums/showthread.php?t=91

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