Watched the video about TR installation a few times and temporarily installed the TR gear box to the air frame. Fitted the drive shaft coupling onto the TR gear box shaft and aligned the pre-drilled holes.I made a steel bushingon my lathe with the OD of a letter D drill and the ID of 7/32". This helps topre- drill the hole very concentricinto the coupling. Next I opened up the hole with a letter D drill and fitted the 1/4" bolt. Next I drilled all the bolts for safety wiring with the provided 1/16" drill.