Shifter bushings are plastic bushings that fit over the end of the shifter that connects to the shift rail. They provide a tight fit and that smooth feel while keeping the shifter firmly in the proper shift rail. When a shifter bushing is worn the shifter feels loose. This is because the worn bushing left a gap between the handle and the shift rail.
Shift rails have detent notches machined into their sides. A spring loaded ball fits into the detent notch to keep the transmission in gear. If the ball slips out of its notch the vehicle will jump out of gear. The shift rail should slide easily in its bore. It should not have any lateral up and down or side to side movement. Check each ball and spring for wear and tension; a weak spring will result in the transmission jumping out of gear.