C4 Maintenance  7. Joint #3 
 
98  C Series Maintenance Manual Rev.2 
Installation: Joint #3 Reduction gear unit 
When tightening hexagon socket head cap bolts, refer to the 2.4 Tightening Hexagon Socket 
Head Cap Bolts. 
 
1. 
Unpack the new reduction gear unit package and check if it 
contains the parts on the right. 
 
Tooth grooves of the circular spline and the flexspline, and the 
bearing of the wave generator are pre-greased.    Wipe grease if 
it is attached to the fitting parts. 
O-ring 
Flexspline 
+Cross roller bearing unit 
Circular spline 
Wave generator 
 
CAUTION 
■ 
Do not adjust the bolts securing the flexspline and the cross roller bearing. 
  If the 
bolts are adjusted, it requires centering of the parts by the reduction gear unit 
manufacturer.
 
2.  Set the O-rings to the grooves on the both faces of the circular 
spline. 
Make sure to fit the rings completely. 
 
 
Convex surface 
Concave surface 
 
Convex surface 
Groove 
Concave surface 
Groove 
 
3.  Set the flexspline with the convex surface facing down. 
4.  Match the screw holes on the cross roller bearing's inner ring 
and the drilled holes on the circular spline.