727 doesn't shift into second gear like it should

I may try to adjust the band, but after seeing the post fishy68 made about band overlap, I think that might be the issue. When it shifts itself, all is fine. But when I manually shift it into second the car will nose dive and bog.
that is CRAZY! my 727 does the EXACT same thing.in drive its shifts great .manually from 1st into 2nd,it bogs down the engine down and acts like it doesnt want to go into 2nd .and then 2nd to 3rd it is fine.wow and i thought i was losing my mind lol. i just got the tranny and motor,and i know nothing about anything being done to the transmission.im glad to find out more info thanks !