Gears and Drive Chain

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 the gear faces and shaft for wear, cracks, damage, and seizure.
Check the surfaces which contact the sun gear, clutch drum, clutch hub, press flange, clutch piston and each bearing for damage, peel, partial wear, dents, bending, or other abnormal damage. If any is found, replace with a new one.

Fig 1: Locating Gear Faces And Shaft For Wear And Cracks
Courtesy of NISSAN NORTH AMERICA, INC.