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Can I leave the passing gear cable disconnected?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 8_YOUR_H2, Jul 26, 2002.

  1. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    I am installing a TH350 and I dont care about the passing gear. But I was reading TCI's website and it said you always have to hook up the TV on a 700 or the passing gear cable on a TH350 to prevent pressure from building up? I know my buddys disconnect theirs and I cant rember them having any problems? Does anyone have any input on this.
    thanks
    Brent
     
  2. Muddytazz

    Muddytazz 1 ton status

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    My dad's is hooked up on his, yet the cable is broken also lol. All he has to do if it starts to lug down is manually downshift and all is good.
     
  3. 95 Silverado

    95 Silverado 1/2 ton status

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    the passing gear cable on a 350 turbo and the cable on a 700R4 perform two entirely different functions. the passing gear cable is just that, it activates the passing gear at full throttle,and that is it's only function. the cable on a 700R4 has complete control over the shifting on that transmission, it won't shift correctly and will be damaged if it is not hooked up.
     
  4. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    I realize the difference between the 2 and I just cant understand why they insist that it has to be hooked up. What do you think about leaving it disconnected?
     
  5. Muddytazz

    Muddytazz 1 ton status

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    well if you leave it disconnected on the TH350, you need to find something to plug the hole or fluid will just flow out like crazy. But the above post is correct, on a 350 it just engages the throttle to automatically kick it into the next lower gear, but on a 700 it controls the whole shifting operation.
     
  6. Redfrog

    Redfrog 1/2 ton status

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    mine has been unhooked for about 4 years and no problems.. it is the orignal tranny W/O a rebuild (that I an aware of) and it seems fine. just a little slow when passing people.... I would say it would be ok just on the basis that mine has not fried yet.... it has about 150-60k on it
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Yeah you can but Mine was discconected for a week and it was hacking me off big time. It takes it's own sweet time down shifting without it. Imagine punching it to get around somebody and the truck won't go cause it won't down shift. The brackets are laying all over the place in the junkyard, not hard to find at all. Much easier to adjust than a TV. Pop the clip to reset it. lock it back in. Give it full throttle once before starting the engine and it's set.
     
  8. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    While we're on the subject of these cables....what's the deal with the "slider" part that connects to the carb linkage?

    A friend taught me the secret to setting the linkage was to unclip that plastic tab on the cable retainer, pull the throttle linkage WIDE open and hold it there(to set the proper slack) while clicking that plastic tab back down in place. I understand all of that, and it made sense to me.

    Then I bring my truck to a shop to have some engine work done, and when I get it back, they have put this little bolt and nut in that "slider" area, to create the effect of a shorter slot???

    It seemed like there was plenty of adjustability in the linkage without this "cheezy" modification, and I find it hard to believe this is what GM intended. Any ideas why some people do this, and if I should remove it?

    This is on a TH350 by the way, not a 700R4.


    "It's not easy being green" -Kermit The Frog
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well that makes absolutly no sense to do that. The Linkage would then just readjust to the new stop point first time you floored it and I doubt it would shift any sooner than it did without it. It's a self adjusting linkage The only thing I can think of is it would cause the adjuster to bottom out. then it would cause it to kick down earlier BUT it may run out of the little bit of spring give it has and eventually break the cable or prevent you from getting full throttle on the carb. Most modulators you can stick and allen wrench in and adjust it. The Kick down and the modulator have to work together to create the kick down when you floor it. If it's not kicking down as fast as you want you usualy adjust the modulator to speed that up not rig the down shift cable.
    Hows does it drive like that. It may actully be a good little trick to get kick down at say 3/4 throttle if there is enough give in the cable. I just have never run accross that before.
    I understand what this guy was trying to do I just not sure it will work how they plannind it to. Hmmmmmmmmm I might play around with mine and see what it does just to see. I got a bud into Hot rodding that was a pro wrench for many years. I'll be seeing him tomorrow and I'll pick his brain a little on it and see if he as ever heard of it before.
     
  10. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Grimmy,

    What's weird is that it seems WORSE with that little gizmo in there.....

    I have a few other problems engine-wise, so I can't conclusively say that this is the ONLY problem, but when I floor it, it seldom even downshifts at all! Feels like I need to press the pedal THROUGH the floor to get the downshift!!!! /forums/images/icons/grin.gif


    Anyway, I will remove the bolt today, and re-adjust that plastic tab thingie....Once the engine is running again, I can do a test drive and collect some more data!
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Yeah if you have any vacume leaks then the modulator may not be getting the correct signal and giving you down shift problems. In fact check that vaume line running to it and pull it off the modulator. Most of the time when a modulator fails it will leak ATF out the vac connection. Maybe this guy was a dolt and didn't know that.
     
  12. rem7600

    rem7600 1/2 ton status

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    Hey Grim,

    Long time no talk but we have...

    I have TH400 that will refuse to shift down to 1 (VERY occasionally I can get it to do it if I am in 2nd). Shifts from 3 to 2 on the second full throttle attempt (to the floor) and I'm extremely frustrated with it. Have replaced the kick down switch and a vacuum something or other on the tranny's side.

    Any thoughts?

    REM7600
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Make sure the electric kickdown thingie is hooked up on the left side of the tranny. Did a TH 400 come in your rig?

    TH 400s use an electric kickdown, no cable for them

    Could also need to adjust that modulator.
     
  14. Pure Insanity

    Pure Insanity 1/2 ton status

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    OK well since were on the subject of kick down.....Mine kicks down fine, the problem I have is that 1st gear wont hold past 3000 when I have my foot to the floor. (The wifes car will tune in 6000 before it shifts.) Normal driving it shifts at 2800-3000, so I am not gaining much by sticking my foot in it.

    2nd gear seems to hold as long as I have held it so far. Ive only had the nads to pull it to 4000 in 2nd. By that time Im moving about 75-80ish and back it down.

    I tried to adjust the cable a while ago before I left the shop. The cable I have is the one that clips onto the carb. Not the slider type. I pushed the "button" to release the cable mount and pulled it back, released the button, and pushed the pedal to the floor. When I test drove it there was no difference. Still shifted at 3000. Any ideas?

    BTW, this is a TH 350. If its a vacuum issue Im prob screwed since my cam doesnt make much vacuum. (Makes stopping fun at times too.)
     
  15. 95 Silverado

    95 Silverado 1/2 ton status

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    along with checking the modulator be sure the line to it is intact, and the vacuum is getting to the modulator, the small line can sometimes kink shut and block the vacuum from the modulator or break off and lose the vacuum altogether. it should be a metal line with small pieces of rubber hose at each end.
     
  16. sinchphoto

    sinchphoto 1/2 ton status

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    a 700 does not have a passing cable. it has a throtlevalve cable. wich activates the shiftting of the transmission. without it youll have no shifting and will fry the tranny.
     
  17. rem7600

    rem7600 1/2 ton status

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    Grim you mentioned adjusting the modulator in an
    above post. Just how does one adjust the modulator?
    I have a TH400 and "believe" it is the part I replaced.
    It has the vacuum line leading into it. Didn't
    appear to be any adjusting about it. Thoughts?

    I'm having bad kick down issues. If I stomp on
    it twice it WILL go from 3rd down to 2nd but only
    to a low RPM point and then it jumps back to 3rd.
    I can't get it to go down to 1st even by trying to
    put my foot through the floor. Vaccuum? Readjust
    the cable link? I'm not familiar with the process.

    Leave it to me to ask the dumbest of questions.

    /forums/images/icons/confused.gif
     
  18. rem7600

    rem7600 1/2 ton status

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    And by the way, the TH400 is in the
    77 3/4 ton, not the 89 Jimmy.
     
  19. rem7600

    rem7600 1/2 ton status

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    Hey Tim,

    Thought I had replied before but don't see it anywhere.
    TH400 is original in rig... BUT motor has been swiped...
    Was a 454 original, now a freshly(20K) rebuilt 305. Not
    the "bestest" performance in the world, but it runs good.
    I've been using the gearshift WAY too much to do my
    downshifting. I'm ready for it to work properly from
    the pedal.

    I will check the electrical connector's on the left side
    of Tranny tomorrow. I replaced the modulator but may
    still have vacuum issues. I saw no adjustments available
    on the modulator, am I missing something?

    Thanks Man!
     
  20. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Here is the email the guy who rebuilt it sent back to me when I asked him this same question

    </font><blockquote><font class="small">In reply to:</font><hr />
    Brent, it HAS to be hooked up AND "set" properly. It controls internal pressure,
    shift points and passing gear. You will burn the clutch plates and band if you do not select the correct cable and have it set properly. The installation should be done by a professional shop

    [/ QUOTE ]

    I guess that answers it...
     

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