automatic tranny upgrade

[Trokita101]

Hi guys,

My bump is 90% road ready, however, the 3 speed automatic tranny is not working properly, its not shifting to third gear. The new dilemma, repair or upgrade to a better tranny what is your recommendations. Thanks

[BobbyFord]

C6? C4?
Either one, make sure modulator vacuum line is secure and has no cracks or leaks.