Thread: 1974 Upshift??

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  1. #1 1974 Upshift?? 
    SE Level Member 74GrandPrix's Avatar
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    Drove the new '74 home.
    Tranny did not want to upshift until engine rpm went high.
    Found a bad vacuum leak where the tranny modulator line hooks to the carb.
    I replaced the short section of vacuum hose with one that fit correctly.

    Will this fix the problem??

    Thanks!
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  2. #2 Re: 1974 Upshift?? 
    Transmission Expert Trannyman95's Avatar
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    Your car likely has a TH400 trans, but may also have a TH350. Fixing the vacuum leak should help out and also make sure the modulator isnt bad-if there is trans fluid in the vacuum line it is bad and will need to be replaced. The modulator has more effect on line pressure than anything but could also be causing your late shifts if you have the TH400 trans.
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