The 1999 - 2004 Grand Cherokee (WJ) does not have an actual VSS (vehicle speed sensor). However, there is a VSS signal generated by the ABS controller which is sent to the PCM. The ABS controller get speed information from the wheel speed sensor signals. I would guess that if the speedometer seems to be working correctly that would probably mean that the the VSS signal is correct.
2001 WJ Limited with Quadra-Drive, Kenne Bell Supercharger, 3-inch Kolak exhaust, Stillen rotors (F/R) and MM pads, Addco sway bars (F/R).