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Author Topic: TH400 shifting problem  (Read 1205 times)

Offline coltonbily

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TH400 shifting problem
« on: April 29, 2018, 05:56:44 PM »
i have recently started driving my 1975 c20 with a 454 and th400. if i put the trans in Drive it starts in 3rd and goes really slow from a stop. i can shift it manually through all the gears but it will not shift automatically, the kickdown does not work and and the vacuum modulator does not suck ATF. i checked the governor and the gear was not stripped and the weights move, all seems to be OK except that it wont shift automatically. ATF levels are fine  ANY SUGGESTIONS?
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Offline Rapid Roy

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Re: TH400 shifting problem
« Reply #1 on: April 29, 2018, 06:22:23 PM »
Welcome.
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1974 Cheyenne 10 LWB STOCK 350 W HEI /TH350/AC/4 BBL Quadrajet
Mopar by Birth
Chevy by Choice

Offline VileZambonie

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Re: TH400 shifting problem
« Reply #2 on: April 30, 2018, 09:32:04 AM »
Possible someone messed with the valve body? I would suggest a transgo shift kit and clean the valve body, make sure everything operates smoothly. Does the governor valve move freely?
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