The bushings on your lower shifter and transmission link are made of plastic. Over time, it wears. You can replace those bushings by BMP's bushing for $40 or use my trick. I hope that last time you replaced your rear shock mounts, you have kept the old ones in a box somewhere, because hell, it could be usefull someday. Well, that day has come. Remove the metal sleeves from the shock mounts. It is a direct replacement for the old plastic bushings on the longer tranny link, and needs to be shorten a bit on the lower shifter. To get a 100% playless shifter, I use thin washers before I put the clips back.
BTW I am also experimenting with bearing shifters. Smooth and no play with a lifetime duration. Will let you know more about it later.