Ok, since I'm at my wit's end, I thought I'd ask for some advice. I have a 350 tranny behind a small block in my '53 Chevy wagon. I just got the car on the road and it's not shifting like it should. I can get it to shift out of first, but I have to rev it in order to get it to work. Everything I've read says it's the vacuum signal that shifts the transmission. So far I've replaced the vacuum modulator, replaced the vacuum line (hardline with VERY short pieces of rubber hose on each end), and backed the adustment on the modulator all the way out. It's better than it was at first, but still doesn't shift anywhere near when it should. The transmission is a fresh rebuild. What am I missing?