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Transimission Not Shifting

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BowtieRed, Feb 4, 2003.

  1. BowtieRed

    BowtieRed 1/2 ton status Author

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    My transmission doesn't slip, and it's tough as hell- but when it warms up it won't shift. This is like after 5 miles. I'll put it in D and it will stay in first gear until I drop it to "2" or neutral while driving. Then it will shift, after a little work. Then if i let the pressure off from the engine it will shift back down. When I drop it to neutral I'm not really stressing it that much, as I got b!tched out for on other sites. I can pretty well match up the RPM with the speed, but the thing is when I put it in "2" or Second gear, it goes to first gear anyway. And won't go to second. A while back My tranny lost sense of all gears and i could move the shifter up and down on the column with it only randomly falling into gears, in no particular order. I found out that the linkage had fallen out of a lever on the chassis between the body and the transmission. That's what I assumed, because it fixed itself at one point. i have a TH350 in a 1978 K5. I've thought solenoid problems- anything else maybe?
     
  2. BowtieRed

    BowtieRed 1/2 ton status Author

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  3. BowtieRed

    BowtieRed 1/2 ton status Author

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    help? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif
     
  4. NightRider

    NightRider 1/2 ton status

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    I highly doubt this isnt the problem but, did you check how much tranny fluid you had in your rig? The other day mine wasnt shifting right and I was low on fluid. Sorry, I'm not a big car person just yet. Only 17 and learnin. Hope you fig it out though.
     
  5. Thunder

    Thunder 3/4 ton status

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    Assuming your linkage is working right............
    The way you describe the problem sounds like the problem may be the Vacume Modulator. Check the vacume line that goes to it. It may have fallen off or have a hole in it. If the line is ok the modulator is probabally bad.
     
  6. BowtieRed

    BowtieRed 1/2 ton status Author

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    ok, assumin i ned a new modulator- how much that gonna run me?
     
  7. Thunder

    Thunder 3/4 ton status

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    prolly around $20.oo. Very easy to install
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    If you ARE having modulator problems, typically when you pull the hose off of it, it will have ATF there. (it's not supposed to) The modulator's are pretty simple, I'm sure a simple "apply vacuum, see if it holds" test will work, and as long as the movement isn't sticky or jerky there, it's more than likely going to be fine.

    Another thing to check of course, is that the line is actually getting vacuum when it should be. I *beleive* the modulator is hooked to manifold vacuum, so you can check this with the vehicle just idling.

    Just a couple of ideas, no point in throwing money at a perfectly good part.
     
  9. bee32

    bee32 1/2 ton status

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    Check your kick down cable as well.
     
  10. BowtieRed

    BowtieRed 1/2 ton status Author

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    Ya'll are way over my head, I'll take a pic and ya'll draw some arrows, ok? Thanks /forums/images/graemlins/grin.gif
     
  11. imiceman44

    imiceman44 1 ton status

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    OK I don't know how much you know in trannies but I would say it's the governor.
    There is a valve in the governor that could be sticking.
    And of course check the fluid level with the engine running at idle in neutral or park.
     
  12. bee32

    bee32 1/2 ton status

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    Check your gov first. If that is okay than look at your kick down cable. The cable can be out of adjustment and it can mess with the shifting. But then I know more about the 700r4's so I might be wrong. Hope it helps. Best advice is get a Hanes manual for GM Trannies at the part store. If can't find one let me know and I will look it up in mine.
     

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