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transmission identification

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by milspecjimmy, Dec 16, 2002.

  1. milspecjimmy

    milspecjimmy 1/2 ton status

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    i have a tranny in my shed that some one told me was a gm rock crusher. i have no idea what it is, or what it came out of. its a 4 speed manual, and its nothing too new. where on the case do i look for identifying #'s or markings?
    thanks
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  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Lets see.

    Muncie 4spds (M20/M21/M22 car trannies) are all aluminum cases as I recall. Shifter stuff on the side.

    I'm sure you can find lots of "rock crusher" (which is ONLY the M22) info online, maybe from Corvette sites. In an original car Muncie tranny, the rings cut into the input shaft would tell you, but too easy/common to change the input shaft, case parts, etc., to be reliable ID, internal inspection would be necessary. Way overused term, seems everyone thinks they have a "rock crusher" under their bed. (not saying you think you do, just what you hear all the time)

    *True* M22's are probably in the vicinity of $2000 anymore, since they were EXTREMELY rare in the first place. It's not like you got one with every SBC 350 Camaro that came out /forums/images/graemlins/smile.gif In actuality, they aren't that great of a tranny compared to what else is out there now (especially for the money) but for someone going the original route, Muncie's are typically the way to go, and most fetch a fair penny.

    Any *truck* tranny worth having (hehe) is a "top loader", meaning no external shift linkage save the shifter handle itself. Apparently the truck tranny was also made by muncie, so there could be confusion there.

    http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1874553615 thats an M20/21 from my limited knowledge, M22's have almost straight cut gears, which is what gave them the name rock crusher, since straight cut gears are noisier than the angled ones shown.
     
  3. milspecjimmy

    milspecjimmy 1/2 ton status

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    the tranny i have is most definately a top loader, and i am hoping it is an sm 465. ill take a few pics and post them on my webshots in a little while.
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  4. wrathORC

    wrathORC 1/2 ton status

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  5. R72K5

    R72K5 Banned

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    47-67 were the years for the 420, they were replaced by the 465 in 68

    one was muncie and other was chevy, 465 have two pto covers and 420 has only one, R is on driver side on 420 and pass side on 465
     

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