I don't have a kick down linkage setup on my carb/ tranny. I'm going to try a band adjustment first. If I leave it in Drive, the transmission will shift OK, it's when I manually go to 1st (L), rev up the rpms and drop it to 2nd gear. It won't shift and continues to rev up until I release the gas pedal. Maybe a vacuum problem with the modulator valve? I don't much about trannies, but I think it may be something I resolve without a tranny shop charging me $ to look at it.