96 GTP Reverse Acting up Need input !

96 Gtp 3.4 105k miles ..auto tranny ...here is the problem
transmission shifts great in all forward gears nice and smooth ...however when i put in in reverse it seems like it is engageing but i have to step hard on the gas pedal to actually move it will jerk hard and car will move if i go easy it feels like it is slipping or not completely enagaged .... fresh fluid and filter at the right level ....im not really sure if i need just some kind of an ajustment or tranny is on its way out

any help would be great

changed the modulator today ..didnt make a difference ....reverse lights do work when put in R should i mess with the switch anyway ? is there anything else that i can ajust ?

dom