Transmission Case: Installation

WARNING: This page is about a different car, the 2021 Subaru Impreza. However, it is still accessible from the selected car via links, so may be relevant.

Wipe off grease, oil and dust on the mating surfaces of transmission cases with cleaning solvent.
Install the reverse idler gear. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>REVERSE IDLER GEAR>INSTALLATION .
Install the shifter fork and rod. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>SHIFTER FORK AND ROD>INSTALLATION .
Select the drive pinion shim. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>DRIVE PINION SHAFT ASSEMBLY>INSTALLATION .
Install the taper roller bearing outer race to the transmission case LH side, and install the differential side retainer with the O-ring removed.
Install the front differential assembly.
Install the main shaft assembly.
NOTE: Align the needle bearing knock pin hole to the transmission case knock pin.
Install the selected drive pinion shims and drive pinion shaft assembly.
NOTE: Align the roller bearing knock pin hole to the transmission case knock pin.
Align the transmission cases with each other, and tighten them with 17 mounting bolts.
CAUTION:
- Insert bolts (11) and (16) from the LH side of the transmission case.
- Match the cases together so that the drive pinion shims are not caught between the cases.
Tightening torque: 8 mm bolt

25 N.m (2.5 kgf-m, 18.4 ft-lb)

* 10 mm bolt

39 N.m (4.0 kgf-m, 28.8 ft-lb)

Fig 1: Transmission Case Bolts Tightening Sequence
Courtesy of SUBARU OF AMERICA, INC.
Install the taper roller bearing outer race to the RH side of the transmission case.
Tighten the bearing mounting bolts.
Tightening torque:

30 N.m (3.1 kgf-m, 22.1 ft-lb)

Courtesy of SUBARU OF AMERICA, INC.

Adjust the backlash of the hypoid driven gear and the preload of the taper roller bearing.

Attach the ST on drive pinion shaft assembly.

Preparation tool:

ST: STOPPER (498427100)

Courtesy of SUBARU OF AMERICA, INC.

Place the transmission case with the LH side facing downward, and put ST1 on the taper roller bearing outer race.

Screw in the differential side retainer from the bottom into LH side case using ST2. Fit the ST3 on the main shaft. Shift the gear into 4th or 5th, and turn the shaft several times. Screw in the side retainer while rotating the ST3 until a slight resistance is felt on ST2.

This is the contact point of the hypoid driven gear and the drive pinion shaft. Repeat the above sequence several times to ensure the contact point.

Preparation tool:

ST1: WEIGHT (399780104)

ST2: WRENCH COMPL RETAINER (18658AA021)

ST3: HANDLE (499927100)

Courtesy of SUBARU OF AMERICA, INC.

Remove the WEIGHT, and screw in the differential side retainer without the O-ring into the RH side of the transmission case using ST, and stop at the point where a slight resistance is felt.

NOTE: In this condition, the backlash between hypoid driven gear and drive pinion shaft is zero.

Preparation tool:

ST: WRENCH COMPL RETAINER (18658AA021)

Courtesy of SUBARU OF AMERICA, INC.

Loosen the differential side retainer on the LH side of the transmission case by 3 notches, and turn the side retainer on the RH side of the transmission case by 3 notches in order to apply backlash.
Screw in the differential side retainer of the RH side of the transmission case additionally by 1 notch in order to apply preload on taper roller bearing.
Temporarily tighten the retainer lock plates LH and RH, and put marks on both the differential side retainer and lock plate for later readjustment.
NOTE: If it is hard to install the lock plates, reverse the sides and install them.
Turn the main shaft several times while tapping around the differential side retainer lightly with a plastic hammer.

Inspect and adjust backlash and tooth contact of the hypoid driven gear. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>FRONT DIFFERENTIAL ASSEMBLY>INSPECTION .
Separate the transmission case. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>TRANSMISSION CASE>REMOVAL .
Check each shifter fork. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>SHIFTER FORK AND ROD>INSPECTION .
Select a main shaft rear plate. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)> MAIN SHAFT ASSEMBLY>ADJUSTMENT .
Apply liquid gasket, then join the transmission cases with each other.
Liquid gasket:

THREE BOND 1215B or equivalent

Courtesy of SUBARU OF AMERICA, INC.
Tighten 17 bolts with brackets and clips as shown in the figure.
CAUTION:
- Insert bolts (11) and (16) from the LH side of the transmission case.
- Match the cases together so that the drive pinion shims are not caught between the cases.
Tightening torque: 8 mm bolt

25 N.m (2.5 kgf-m, 18.4 ft-lb)

* 10 mm bolt

39 N.m (4.0 kgf-m, 28.8 ft-lb)

Fig 2: Transmission Case, Brackets And Bolts Tightening Sequence
Courtesy of SUBARU OF AMERICA, INC.
Tighten the bearing mounting bolts.
Tightening torque:

30 N.m (3.1 kgf-m, 22.1 ft-lb)

Courtesy of SUBARU OF AMERICA, INC.
Remove the retainer lock plate, and loosen the differential side retainer until the groove of the O-ring appears. Fit a new O-ring into the groove and tighten the side retainer into the position where it was not loosened.
NOTE:
- When loosening the side retainer, record the number of the turns made.
- Perform this for both left and right side retainers.
- Apply transmission gear oil to O-ring.
Install the retainer lock plate.
Tightening torque:

T: 25 N.m (2.5 kgf-m, 18.4 ft-lb)

Fig 3: Retainer Lock Plate Bolt (With Torque Specification)
Courtesy of SUBARU OF AMERICA, INC.
Install the transfer case together with the extension case assembly. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>TRANSFER CASE AND EXTENSION CASE ASSEMBLY>INSTALLATION .
Install the clutch release lever and release bearing. Ref. to CLUTCH SYSTEM>RELEASE BEARING AND LEVER>INSTALLATION .
Install the manual transmission assembly to the vehicle. Ref. to MANUAL TRANSMISSION AND DIFFERENTIAL (5MT)>MANUAL TRANSMISSION ASSEMBLY>INSTALLATION .