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Old 09-26-2019, 05:53 PM   #1
67Vega
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Join Date: May 2019
Location: Clarksville Tennessee
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Please help with my transmission

Hey guys, so I recently replaced my working harness on my 67 GMC C1500 truck. She turns over and runs semi fine, but there are 2 connections that were left with nothing connected to em. The first one is on the transmission, it's on the left side in the middle of the tranny, single prong. I don't know what it connects to. The second one is under the carburetor, and it's a 2 prong connection. I also don't know what it connects to. And lastly, I replaced the steering column on it, and I can't get it to shift right. Neutral on the column is reversed on the transmission, Drive is nuetral, and 2 is Drive. Also, reverse lights come on while not in Reverse for the transmission, comes on between Nuetral and Drive on the steering column. I've pulled the shift fork all the way up into the Park position, and secured it to the steering column all the way up in the Park position indicator. Nothing is working with it. What can I do to fix this issue. Thanks in advance. Also the transmission is a TH400.
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Old 09-26-2019, 06:06 PM   #2
AussieinNC
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Re: Please help with my transmission

The single wire terminal on the side of the trans is for the kickdown function....

If the terminal had two wire connectors, one is kickdown and one is convertor lockup...
Single terminal...non lockup
Two terminals...lockup convertor

TH400 trans do not use a "kick down" cable....

The switch on the carb is the kickdown switch itself,,,,

it is sometimes on the carb and sometimes on the pedal under the dash...

Hope this helps

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Old 09-26-2019, 06:22 PM   #3
67Vega
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Re: Please help with my transmission

Thanks for that info. But, by chance would you know how they are connected?
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Old 09-26-2019, 06:37 PM   #4
AussieinNC
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Re: Please help with my transmission

For the trans to have a kick down function, the single terminal on the side of the trans needs a 12v signal source under full throttle conditions.

1/ Engine Off...First check the switch on the carb is working correctly....put a multi meter set to ohms across the two terminals and with the throttle at rest the reading should be open circuit...

If its open circuit, then open the throttle fully (engine off) and the switch should now read zero ohms (short circuit)...

2/ Check the solenoid in the trans is working...engine off, supply 12v to the single terminal...you should here a faint click from inside the trans...

If both of the above conditions are met...run a single wire from single terminal on trans to one of the terminals on the carb bracket....then supply a switched 12v supply voltage to the other terminal on the carb switch...

A simple diagram is attached...

Hope this helps
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