A 98 grand cherokee with 4.2L? I know the 4.0L, 5.2L or 5.9L. Or is it not the original engine?
I would first have a look if the shifter cable is attached to the transmission lever and if nothing is wrong with the cable. It should not feel soft.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.