Except For STI Model

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

Apply grease to the shaft sliding surfaces of the internal gear assembly.
Grease:

Multemp #6129 or equivalent
Assemble the shaft to the internal gear assembly.

Fig 1: Separating/Connecting Internal Gear Assembly And Shaft
Courtesy of SUBARU OF AMERICA, INC.
Assemble the overrunning clutch as follows:
1. Apply grease to the spline portion of the shaft.
  Grease:
  
  Multemp #6129 or equivalent
2. Install the overrunning clutch to shaft.
  
  Fig 2: Removing/Installing Shaft Overrunning Clutch
  Courtesy of SUBARU OF AMERICA, INC.
3. Pass stopper (B) through the shaft assembly, and attach snap ring (A).
  NOTE: Use new stoppers and snap rings.
  
  Fig 3: Attaching Snap Ring
  Courtesy of SUBARU OF AMERICA, INC.
4. Using a press, pressure fit stopper (B) into snap ring (A).
  
  Fig 4: Pressure Fitting Stopper Into Snap Ring Using Press
  Courtesy of SUBARU OF AMERICA, INC.
Assemble the overrunning clutch, internal gear assembly, shaft and shift lever as a single unit into the starter housing assembly.
NOTE: Apply grease to the moving parts of the shift lever.

Grease:

Multemp #6129 or equivalent

Fig 5: Disassembling/Assembling Overrunning Clutch, Internal Gear Assembly, Shaft And Shift Lever
Courtesy of SUBARU OF AMERICA, INC.
Apply grease to the inside of the internal gear assembly and pinion gear, and attach the pinion gear to the internal gear assembly.
NOTE:
- Apply grease evenly to the contact surfaces of each gear.
- Be careful that no debris becomes attached.
Grease:

Molykote® AG650 or equivalent

Fig 6: Identifying Pinion Gear And Internal Gear Assembly
Courtesy of SUBARU OF AMERICA, INC.
Install seal rubber (A), plate (B), and seal rubber (C).

Fig 7: Removing/Installing Starter Seal Rubber And Plate
Courtesy of SUBARU OF AMERICA, INC.
Assemble the armature assembly to the yoke assembly.

Fig 8: Disassembling/Assembling Armature And Yoke Assembly
Courtesy of SUBARU OF AMERICA, INC.
Attach the armature assembly and yoke assembly to the starter housing assembly together as a single unit.
NOTE: As shown in the figure, match the protrusion of the yoke assembly to the cut out of the starter housing assembly.

Fig 9: Matching Protrusion Of Yoke Assembly To Cut Out Of Starter Housing Assembly
Courtesy of SUBARU OF AMERICA, INC.

Fig 10: Identifying Armature And Yoke Assembly
Courtesy of SUBARU OF AMERICA, INC.
Use an appropriate tool (such as correctly sized socket wrenches) and attach the brush holder assembly to the armature assembly.
NOTE: Be careful not to damage the brushes.

Fig 11: Identifying Brush Holder Assembly
Courtesy of SUBARU OF AMERICA, INC.
Secure starter cover assembly to the brush holder assembly with screws (A).
Tightening torque:

1.4 N.m (0.1 kgf-m, 1.0 ft-lb)
Install through bolts (B) on both sides.
Tightening torque:

6 N.m (0.6 kgf-m, 4.4 ft-lb)

Fig 12: Identifying Brush Holder Assembly Mounting Bolts
Courtesy of SUBARU OF AMERICA, INC.
Attach the magnet switch assembly to the starter housing assembly.
Tightening torque:

7.5 N.m (0.8 kgf-m, 5.5 ft-lb)

Fig 13: Locating Starter Housing Assembly To Magnet Switch Assembly Mounting Bolts
Courtesy of SUBARU OF AMERICA, INC.
Attach the cable to the terminal M of the magnet switch assembly, and secure with nuts.
Tightening torque:

10 N.m (1.0 kgf-m, 7.4 ft-lb)

Fig 14: Identifying Magnet Switch Assembly Terminal M
Courtesy of SUBARU OF AMERICA, INC.