Just got an answer from my brother who owns a '99 4.0 ltr. GC . He had swapped the original trans (42RE?) for what he said was the same trans from an earlier GC 4.0 ltr. , a ZJ but yours being a WJ , he says they are the same. To swap the throttle valve cable , on the trans , unsnap the cable end from the throttle valve lever . It is a metal ball that the plastic cable end pops on to on the lever and the cable housing snaps onto a bracket mounted to the trans. You unsnap the cable housing by slipping an open end wrench the right size to squeeze two clips inward to slip out of the bracket . Move up to the engine , done much the same way. Dismount the cable housing from same bracket accelerator cable mounts using open end wrench but the plastic end of cable slips off of throttle linkage by unsnapping it . So you would not pop this one off , you slide it off . Replacing , engine side of cable slides on and snaps onto accelerator linkage and trans side of cable will pop onto metal ball. The cable housing on both trans and engine just easily slip through brackt(s). Adjusting TV cable : there should be a removeable clip that locks cable housing to cable sheath to hold adjustment . Remove clip , have someone hold accelerator to floor (engine off , of course) snap clip back on. Done. Test drive to ensure trans is shifting correctly , if not , readjust again. This adjustment is crucial and must be done right for trans to shift correctly or overheating and damage will occur. Post back if unsure of any procedure.
Do not jeopardize a good trans with improper adjustment if uncertain.