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TH350 tranny shifting ?s

Discussion in 'The Garage' started by hawglet, Dec 29, 2004.

  1. hawglet

    hawglet 1/2 ton status

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    Okay, I just got done swapping out a 700R for a TH350 in my Blazer. The only thing is that when it finally decides to shift into 2nd gear it slams and slams into third also but not quite as hard. It doesn' tshift into 2nd until very late, and doesn't really seem to downshift like I think it should. Could the problem be with the vacuum module not getting enough vac. I was told to hook it to a tee on the manifold between the carb and distributor, however, this wan't there so I improvised and hooked it up to the top-front vac. port of the carb. Maybe there isn't enough there to get it to shift low in the rpms then when it does it slam because of the force of the rrrrrrrrr's. Is my thinking correct or should I trash this tranny, I;m sure I can find a tee to put into the spot on the intake. What to do?
     
  2. sweetk30

    sweetk30 professional hooker Premium Member

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    do like thay say

    remove the plug and put in a barb fitting at the spot on manifold . possible wrong port at carb hookup. sounds like its shifting off the govener. if that dont fix check for bad modulator.
     
  3. JIMMY76

    JIMMY76 1/2 ton status

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    Yup Thats What It Sounds Like Lack Of Vacum Thats What Mine Did When The Line Came Off
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    You need manifold vacuum

    You need to hook it to manifold vacuum,directly to the manifold--dont
    "tee" it in with any other hoses(the distributor usually has ported vacuum,exactly the opposite of the desired manifold vacuum)..Hooking it up to the port on the carb probably wont work properly,that port might be for an EGR valve that gets ported vacuum,or is controlled by throttle opening--or it might just be a vent that has NO vacuum!!..

    If the modulator gets no vacuum,it will drag out the shifts to the redline,and slam into the next gear,and sometimes wont shift into 3rd,and will feel like its "freewheeling" when you coast with your foot off the gas....if it doing that,you can bet its probably not getting the correct amount of vacuum,and needs to be hooked up right...:crazy:
     
  5. hawglet

    hawglet 1/2 ton status

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    Thanks to all...

    That is exactly what I was suspecting but not sure. Thanks for the input. Glad to hear.
     

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