Transmission issues automatic overdrive on 1991 Buick Century

My transmission seams to go through alot of fluid but I can not see any evidence of a leak under the car. I put a half quart every 50 or so miles. When it is low it will not shift into third gear. Also it shifts hard into second gear. I just bought the car so I do not know the history of it. Where could the fluid be going?

Asked by for the 1991 Buick Century
It's has to be coming out somewhere check the lines, pan gasket and look to see if there is any wettness around the axles because there are seals behind there also look around the area where the dip stick tube goes into the trans & last but not least the front pump seal.
Thanks, I will take a close look at those areas this weekend. May be can zero in on something.