Sun Gear

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.

Check if oil passage of sun gear is clogged. For this, try to pass a 3.6 mm (0.142 in) dia. wire through oil passage as shown in the figure.
Check sliding/contact surface of each gear, bearing and others for damage, burrs, partial wear, dents, and other abnormality. If any is found, replace sun gear with new one.

Fig 1: Inserting Pin Into Sun Gear Oil Passage
Courtesy of NISSAN MOTOR CO., U.S.A.