Shown is a genuine Warn Overdrive, but modern versions are available from Advance Adapters and ATV Manufacturing. These overdrives are incredibly strong for their size, but most were sent to their doom from improper installation. Shown at bottom is the special drive nut (star-shaped center) and four-corner snap ring that secures the bowl gear to the transmission output shaft. After torquing the drive nut to 100-120 lb-ft, you need to install the special snap ring. Most installers booger up the drive nut or don’t get the snap ring correctly in its bore, which ultimately allows the bowl gear to back off the output shaft, destroying gear teeth as it goes.