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- - Th400 not shifting to third. (https://67-72chevytrucks.com/vboard/showthread.php?t=815331)

Big70

12-06-2020 12:02 PM

Th400 not shifting to third.

So I’m in sacramento ca looking for a shop to take my truck with th400 not going into third. I want to get it looked and maybe even rebuilt. I just hooked a Ben modulator line up and got nothing still not shifting don’t know what to do. How much is the going rate of a th400 rebuild?

Steeveedee

12-06-2020 03:02 PM

Re: Th400 not shifting to third.

Pull the vacuum line off the modulator and see if there is oil leaking there. It could just be that the modulator is bad. If it shifts into second, is it late and harsh? That is also an indication of a failed modulator. Also, for completeness, make sure the trans is full of fluid.

kwmech

12-06-2020 03:07 PM

Re: Th400 not shifting to third.

Make sure you have full manifold vacuum there also

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