Jeep grand Cherokee transmission issues

First, recheck the transmission fluid level while the engine is running. If the transmission worked before you did this, then there is a problem with how the transmission filter was installed, May not be pushed & seated all the way up. Also I see like 4 different transmission filters for this, hope you got the right one.

incorrect fluid will do funny things too.

First of all only use ATF +4 fluid. You probably have the 545RFE tranny. And yes there are two filters for this tranny. One kit must have the deep sump tube in it because of the deeper pan with 4 x 4 option. Then there is a little seal that needs to be seated correctly in the tranny case for the pick up tube. If not seated it will suck air and starve the tranny for fluid. It will eventually throw a code saying incorrect gear ration or governor pressure low. and yes the tranny has to have sufficient fluid to shift and engage correctly. There are no bands in this tranny . Only clutch packs and pistons. and this is a very reliable tranny.