Turbo 400 won’t shift into 3rd

[68350]

Im gonna try to dig into this today but figured I would get some ideas from other members here. I have a 68 impala I purchased a little while ago. It has a 327 with a turbo 400. The trans is supposedly only 5 years old approx with a few thousand miles. It will not shift into third unless you let off of the gas when youre driving. It will coast in 3rd that way, but as soon as you give it gas again it kicks it back into 2nd. Im gonna start with the obvious and make sure the vacuum line is in good shape running down to the module. If its not that, could it be the module or governor? Im hoping its something simple since it shifts into 3rd kind of

[Steeveedee]

First, make sure that the trans is full, and that the vacuum line is attached at both ends. Then pop the vacuum line off the modulator at the trans and see if fluid is leaking. It sounds like the modulator is bad, but could just be a vacuum hose.

[68350]

Thank you!