85 Caprice won't shift out of 1st

I just did a tranny filter service on my 85 caprice, 305 with OD tranny. After the service, which was just filter and fluid, it wont shift out of 1st gear until about 25-30 MPH, and shifts hard. What could this be???

most likely low fluid level. check the level idling in park after driving a few miles.

if its not that check your kickdown cable on your carb

Make sure you didn't bend or jam the throttle valve mechanism. The easiest way to check it is at the carb. The cable should be retracted as far as possible. If you pull on it, there should be spring tension and it should pull back when you release it. Otherwise, the mechanism is probably jammed in some way, most likely at the valve body, since you just had the pan off. If you're lucky, the link between the cable and bellcrank snagged inside the cable housing and can be fixed without dropping the pan.