The drive shaft is placed in the center of the shaft the module rotates on. In most systems there are two bearings hold the drive shaft. There should also be a system to hold the shaft the module pivots on. if your confused about this you should look at 221's Swerve system Revolution swerve
http://www.andymark.com/ProductDetai...ctCode=am-0760
They have one of the more reliable swerve systems around