Any transmission guru's out there. I am new to this as far as posting info so hope this is coorect way. I have a turbo 400 in my Henry J that now does not want to shift until I hit very high RPM, near 6,000. Prior it functioned normally, with a manual/auto setup. Does not seem to be slipping. Fluid level is good. I am wondering if the small piece on the side of the tranny that the vacuum line goes to has anything to do with the shifting? Should I change this out before going ahead and removing the tranny for service?

Thanks !!!