1989 grand marquis transmission issues

I was wondering if anyone can tell me where the cap is to add transmission fluid to my car. i check the levels and need to add some but can't figure out where? Please Help!

There is no cap. Where you checked the level of the fluid is where you add the transmission fluid. Did you check the fluid when it was running and the engine warm, transmission in park? You will need a funnel to put the fluid in.

And when way2old says engine warm, he really means ATF up to normal operating temperature (about 150-180F). I find that in the cold winter weather (below 40F), it can require up to 25 minutes of city driving. Summer requires about 15 minutes of city driving.

And remember to run the transmission through all the gears prior to checking the dipstick,including reverse.