What will cause a 94 Olds Cutlass to suddenly develop a problem shifting from first to 2nd gear?

something i discovered with my 1994 cutsup, it shifted roughly from 1st to second. i drove it for a month like that, until i changed the air filter. i removed the plastic box the air filter sits in to vacuum it out, and i saw that a hose (in charge of vacuum-shifting) was loose. the idiot before me had used a garden hose and some rubber bands. i replaced it with a brake cylendar hose off of a 1987 Pontiac lemans, and it cured the problem, no leaks, no low fluid.

hopfully it is just low transmission fluid or a cloged filter. I would check the fluid level (when eninge is warm)1st. if the level is fine, change the transmission fluid and filter if it has been over about 45K miles since it was last done.