transmission won't down shft, please advise

[bigcarguy]

Like the subject says, my transmission won't downshift. When I go around a turn the transmission just stays in high gear and struggles to get back up to speed. Also never shifts into any kind of passing gear. Is there a way to adjust the tranny kick down cable on the carb? The cable's on there, but there's enough slack where the throttle linkage just moves in the groove and never really pulls on the cable. I know the tranny's fine because it was just rebuilt a year or two ago.