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Attn: Tranny guru's got a little problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BowtieBlazer, Dec 23, 2004.

  1. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    On my daily driver its a c-10 350/TH350. I'm running the original tranny its up around 200k now and I knew it was coming upon its time soon but I wasn't hoping for two days before christmas. I'm suspecious of it being something other than burnt clutches. The fluid is full and clean, still a red not a brown color i had serviced it last about 5 months ago. If I manually shift from first to second to drive it shifts, if I just leave it in drive it will ride the hell out of first gear until I manually shift back into first and then up to second, then it will ride second until I shift to drive.

    Also this is the first cold weather we've had all year the high today is like 37, and its supposed to get down in the 20's tonight....burrrr..... :xmas: dunno if the cold has a part to play. It doesn't change with the amount of time I drive it, and it just started this today out of the blue.
     
  2. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    sounds like a mudulator problem. on the th350 its on the rear pass side of the tranny, it has a vacuum line going to it. check the vacuum line all the way to the engine making sure there are no cracks or holes.

    if the line is fine, you need to replace the modulator. you can get it at any parts store, usually around $15.
     
  3. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    i just went and checked, two things, cracked vacume lines up top, and its hard to tell how it mounts on the bottom side but its not right...might be on to something :crazy:

    thanks for the tip
     
  4. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    A cheap fix, first i'd replace that line or the hoses..
    Mine is a hardline bent from the tranny up to the back of the intake manifold.. Then it just has 2 short lengths of rubber vacuum hose to connect that hardline to the vacuum source on the manifold and the vacuum modulator on the tranny..
    I had to put a hose clamp on the modulator side because it kept on rattling and vibrating loose, and would do very late shifts if at all kindof like you are describing.
     
  5. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    I went up to work and grabbed a new piece of line for the modulator side of the metal line and another 2 small pieces for up top and its back to shifting fine, mine was also T'ed in from the manifold to the cruise control module...



    Its fixed!
     
  6. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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  7. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    glad you got it fixed :waytogo:
     

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