you can make gears with Execute GRIP option in UG.
this gear making program (gear.zip) was tested in ug5,ug7 and ug8.
but, maybe that'll be available other ug version.
tutorial making gear.
Answered with a tutorial: https://grabcad.com/tutorials/how-to-make-gear-in-ug8-ug5-ug7
it is useful but how to genrate grx file
it works spur gear only
YES IT'S USEFUL