Sun Gear

WARNING: This page is about a different car, the 2013 Nissan Armada. However, it is still accessible from the selected car via links, so may be relevant.

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

Fig 1: Checking Sliding And Contact Surface Of Gear And Bearing Using Pin
Courtesy of NISSAN NORTH AMERICA, INC.