Issue: th400 not shifting correctly. Feels like when the truck shifts into 2nd that first gear does not disengage.
Additional information: I never used this transmission before so I do not know the history of the trans. Also, I did do a complete rebuild including installing a 4l80 direct drum and 32 element sprag. It does need to be said that this is my first trans rebuild and I easily could have messed something up.
I did replace the vacuum modulator and ensured the vacuum line is coming from manifold vacuum. Any help is greatly appreciated.