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sm465 tranny rebuild

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by madmike, Jan 24, 2002.

  1. madmike

    madmike 1/2 ton status

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    I replaced the SM465 tranny in my 1980 Chevy truck because it was difficult to downshift from 3rd to 2nd (it was like that when I bought the truck ten years ago). The SM465 I swapped in a couple of years ago came from a 1980 Blazer, and it has the same problem, but not as bad. The transmission also leaks oil from the tranny to the transfer case, when I check the levels, the tranny is low and the 'case is overfull. I know the SM465 has a good reputation, my Dad has one in his truck that shifts sweet, an old man neighbor of mine had one in his truck that I drove and it shifted sweet too. It seems to me that maybe the prior owners of these two trannies I have may not have learned to shift gears in a real truck transmission. Since I will be doing the big block/big torque swap soon, I would like to freshen up a good trans too. I have two questions: does anyone else have similar problems with their 4 speeds, or did I just inherit trannies shifted by non-shifting dorks? I would like to attempt the rebuild myself, it doesn't look that difficult. Can anybody point me in any good direction on shop manuals, advice, photos, special tools that may be required? I would appreciate any thoughts on this...

    [​IMG]psychoholicslag
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    My SM 465 is also hard to downshift to second until it gets below 15 MPH or so. Both my SM 465's are like that and as far as I know it's normal. The speed it will downshift at is dependant on the gear raito/tire size. When I had 2.73's and 33's it would downshift easily at 20 MPH, when I swapped to 3.73's that changed right away.

    As for the leak, there is a seal at the rear of the T-case adaptor that probably needs replacing.

    You could tear down the SM 465, but I doubt you'd find anything wrong with it.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Mine is tough to upshift 2-3. I'm almost 100% positive it is something in the top plate, it feels like it's going into second, but in actually, its going in between 1st and 3rd,which of course grinds.

    Similar problem getting into second to leave from a light, sometimes the shifter goes back, far enough that it FEELS its in gear, but again its not, and just grinds. That one I've gotten used to, but neither IMO is inherent in the design. When the tranny isn't really in second, and I can feel it, I have to REALLY yank back on the stick for it to "break through" whatever is blocking its travel. Never had the shifter assembly apart, but I believe they have small balls that fit into grooves on the shift rails, and I bet somethings screwed up in there.

    My dads behind his 454 shifts really smooth, he says mine just isn't broken in yet : ) ..his is from '74 and has more miles on it (over 200k) than my '76's.

    Mine leaks from the adapter/tranny gasket, but not much. New seal didn't fix it, and the bolts don't seem to like to stay very tight.

    I plan on picking up a spare to play with...throw some new synchros in it, new bearings, make sure the thing wasn't run dry, nor any gears are broken, and make sure the shift parts are in good shape. Problem is finding a 4wd one that is reasonably priced. 2WD ones are dirt cheap ($5 at swap meets lol) but that doesn't do me any good to end up with more down time.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  4. m j

    m j 1/2 ton status

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    the fluid swap thing is a knicked seal between the 2 boxes, BTDT now when i install I do the TC to adapter on the ground and fight with the tranny to adapter powerlift thing. harder to do as you have to support the tranny without a crossmember but I nicked 2 seals in a row and dont wanna do that again.
    your shift problem may be that you are not used to the incredibly wide gear spacing between those 2 gears, do you use the clutch? if you do it clutchless you will soon realize the load you were forcing the brass blocker rings to absorb to bring the gears up to an even speed.
    chev also used a stupid attachment method on the shift forks for the wearing plastic isolators, the forks are dipped in a resin or something so once that peels off you have to buy new shift forks or live with the fact that you can not really get full gear engagement.

    formerly 77chev
    still a jerk though
     

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