727 doesn't shift into second gear like it should

Your describing 1st to 2nd shift overlap. The rear band is hanging on too long when the front band applies. As Kim asked, did he install a shift kit or do any mods himself?

Have you tried getting on it in drive to see how it shifts then? If it's the rear band is hanging on too long it won't act up in drive cause it's not applied in drive, only when you pull the shifter down into low is the rear band applied.