Hard shift to 2nd and 3rd

I'm not going to get into a contest of "I know more than you do because I have papers that say I do" because it's childish but as I stated earlier it sounds like it has a shift improver kit installed, but even if a kit is installed, if the throttle pressure linkage is backed off just enough to lower the throttle pressure just enough to soften the shift (and I know from experience it can be done) but not so much as to lower it to where the shift is mushy or causes flare-up and goes right into 2nd and 3rd at under 15 mph at light throttle it'll be fine. Will it shift like a stock transmission? No... But if you don't mind a firm shift (but not teeth jarring) most likely all you have to do is carefully tweak the throttle pressure linkage a little at a time until it's where you want it. Generally all you have to back it off is 1 or 2 turns. I don't know where some guys get that once you install a shift improver kit it disables the throttle pressure adjustment (which affects shift firmness) but some seem to think it does.

BTW: Passing gear is when you put the pedal to the floor and it kicks down to 2nd gear (or 1st gear if your going slow enough) to give you quicker acceleration. The throttle pressure rod controls a valve in the valve body that works in conjunction with the governor and the more throttle pressure you give it the higher the shift points are and if you back it off too much the governor overrides the throttle pressure and won't let it drop back down a gear when you floor it.

The throttle pressure also directly affects the pressure to the clutch packs and front servo. By doing that the shift firmness can be altered. If a pressure regulator gauge is installed into the main line pressure port on the trans. (the one located between the servos) and you run the engine in drive and move the throttle pressure lever back and forth you can see the main pressure raise or lower. This is what affects shift firmness, and timing.