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  1. #1

    Default 1969 gmc half ton 2 wheel drive.

    I am trying to figure out what type of 4 spd manual transmission my new truck has in it and i found numbers on the left side of the transmission but i can not find any info on it. does someone have a good website to go to for identifying transmissions.

    thanks tony
    Tony-1999 Chevy 1500 z71 4x4

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  3. #2


    I don't know of a website myself, but your trans. is most likely an SM465. It is a heavy old "granny low" 4speed that was used in 1/2 tons up to the C60's. It will have a PTO port on one side (can't recall which side - I'll have to look at one). Reverse is to the right and back. Chevy did have some "oddballs" in a few (VERY rare)or someone could have installed an automotive 4 speed. The SM465 has the shifter on top of the tranny, automotive trans. would be on the side. Hope this helps. KEN

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  5. #3


    Wikipedia has actually do a great job cataloging GM parts like transmissions and engines. Look up manual gm transmissions or just GM transmissions and they will have a list of different trannys and usually what models they came in.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
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  7. #4


    reverse is to the left and down. on the left side of the trans there is a cover with six bolts in it. it is not factory the person that i got the truck from said the truck originally had a 3 on the tree in it.

  8. #5


    OK, ya made me go out and look ! The SM465 has the to the right and back (down) reverse & PTO covers on both sides. I have a much older trans, an SM420, it has the left side only PTO cover and the left and back (down) reverse position. The SM465 main case is close to 12 1/2" long. and the SM420 is 10 1/2" long. Measurements don't include the extension housings. The SM420 was used from about 1948 through the 1967 models, however contrary to common belief, there were some '68 models with the SM420. Nothing wrong with the SM420, I used one in my Willy's pickup for years and we still have an operable "54 chev farm truck with it. It isn't as strong and the synchronizers are a little "crude" and there is a bit more gear noise - especially in 1st. Might be a problem getting some parts for the 420 but I changed the bearings and seals in mine several years ago and got them all from an industrial bearing supply store. I would still be using it in the Willy's but I couldn't get a strong enough transfer case adapted to it without shattering my budget, so I swapped in an SM465. Or rather swapping in the 465, still have to built a new tunnel cover to cover up that monster !! I suppose it is possible for you to have something else but I don't know what it could be. Hope this helped. KEN

    - - - Updated - - -

    Just thought of something else unique to the SM420. The bottom two trans. to bellhousing bolts go in from the bellhousing side.

  9. #6


    I was thinking he might have a Saginaw 4 spd from a passenger car, it was an easy and popular swap back in the day for trucks that werent seeing duty as a fultime work vehicles. This swap became popular in the 70s when fuel became an issue because saginaws had a wider ratio and better final drive.
    Or it could be an M20/21/22, again passenger car trans but in the case of the M22 it has a good rep for taking abuse.

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