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SERVICE BULLETIN
APPLICABILITY:
SUBJECT:

NUMBER: 03-74-14

2015 WRX STI
Gear Oil Leaking from Rear Differential Cover

DATE: 08/18/14

INTRODUCTION
This bulletin provides a repair procedure to address a customer concern of a gear oil leak from the rear
differential cover area. As with any diagnosis, begin by confirming the source of the leak. This will
involve thoroughly cleaning the contaminated surfaces of all residual gear oil and the application of a
suitable leak tracing developer such as Castle® Leak Tracer Powder™ or similar. If the source of the
leak is confirmed as the breather vent assembly which is pressed into the aluminum rear differential
cover, both the cover and the breather vent will require replacement. In some cases, you may find the
breather vent is visibly not fully or evenly seated while in others, it may appear flush. Proper seating
of the breather vent is not the criteria for replacement of the vent and cover. Rely on the results
of your leak tracing to determine what repair is required. While this bulletin addresses a specific
possible leak source, if your diagnosis leads to a different source, repair that condition by following the
applicable Service Manual information.

Accumulation
of Oil (NOT
Source of Leak)

Breather Vent
(Source of
Leak)

COUNTERMEASURE IN PRODUCTION
A change to the breather vent installation procedure was made in production July 21, 2014 starting
with VIN F9812950.
Continued...
CAUTION: VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD
RESULT IN SERIOUS INJURY TO THOSE PERSONS OR TO OTHERS.
Subaru Service Bulletins are intended for use by professional technicians ONLY. They
are written to inform those technicians of conditions that may occur in some vehicles,
or to provide information that could assist in the proper servicing of the vehicle. Properly
trained technicians have the equipment, tools, safety instructions, and know-how to
do the job correctly and safely. If a condition is described, DO NOT assume that this
Service Bulletin applies to your vehicle, or that your vehicle will have that condition.

Service Bulletin Number: 03-74-14; Date: 08/18/14

SUBARU OF AMERICA, INC. IS
ISO 14001 COMPLIANT
ISO 14001 is the international standard for
excellence in Environmental Management
Systems. Please recycle or dispose of
automotive products in a manner that is friendly
to our environment and in accordance with all
local, state and federal laws and regulations.

Page 1

PART INFORMATION
The following list of parts will be required to perform the rear differential cover replacement:
PART NAME

PART NUMBER

QUANTITY
REQUIRED

Cap, Breather

38354AA020

1

38316AA061

1

38353AA050

1

Gasket, Drain Plug

803920050

2

Self-Locking Nuts

902350027

4

Exhaust Gasket

44022AA123

1

Self-Locking Nuts

802008270

2

Gear Oil

SOA427V1800

1

Cover, Differential
Carrier
Gasket, Differential
Carrier

NOTES

n/a

1 for Drain Plug, 1 for Temperature Sensor
These are all one-time use hardware items
which require replacement when removing
the rear differential assembly.
Case of 12, 1-quart bottles. (See more
information at the end of this procedure.)

SERVICE PROCEDURE / INFORMATION
The repair for this condition involves replacement of the rear differential cover and gasket along with
the installation of a new breather vent assembly.
•

Remove the rear differential assembly from the vehicle following the procedures outlined in
the applicable Service Manual.

•

To make it easier, CAREFULLY remove the 2 mounting studs from the original cover
BEFORE removing the cover, as they will need to be changed over to the replacement.

Continued...
Service Bulletin Number: 03-74-14; Date: 08/18/14

Page 2

•

Drain the gear oil then remove the original cover and thoroughly clean and inspect the gasket
sealing surface differential case for any irregularities.

•

Fit the new gasket to the cover as shown. Reinstall the 8 cover mounting bolts and torque to
44 Nm (32.5 ft. lbs). NOTE: The new gasket goes on “dry” with NO SEALER.

Continued...
Service Bulletin Number: 03-74-14; Date: 08/18/14

Page 3

•

Clean and transfer the drain plug into the new cover and install a new sealing gasket. Torque
the drain plug to 60 Nm (44.3 ft. lbs.).

•

Reinstall the 2 differential assembly mounting studs into the new cover until they bottom out.
DO NOT OVERTIGHTEN.

Continued...
Service Bulletin Number: 03-74-14; Date: 08/18/14

Page 4

VERY IMPORTANT: When installing the new breather vent assembly into the rear cover, DO
NOT tap on portion “A” shown in the illustration below. The square drive end of a 12mm ½-inch
drive deep-well impact socket fits over and past portion “A” down onto the “flange” portion “B” and
makes an excellent installation tool / driver.

NOTE: The new breather vent assembly is also installed “dry” with NO SEALER. CAREFULLY
tap the new breather vent into the cover while keeping the impact socket (installation tool) square
and perpendicular as shown in the photos below. The tapping sound will change when the flange
portion of the breather vent bottoms out and is fully seated (no gap) against the rear cover.

No Gap

Service Bulletin Number: 03-74-14; Date: 08/18/14

Page 5

•

The rear differential assembly is now ready for reinstallation into the vehicle in the opposite
order of removal. REMINDER: The 6 self-locking nuts are one-time use and must be
replaced.

•

After installation, fill the rear differential assembly with the required Genuine Subaru 80W90
LSD Gear Oil. The part number to use for ordering purposes is: SOA427V1800 (which is a
case of 12, 1- quart bottles). Two (2) 1 quart bottles may be claimed when performing this
repair procedure. (Actual fill amount is 1.1 quarts.)
*Use part number SOA635302 when claiming these 2 quarts of LSD Gear Oil.

•

Install the gear oil temperature sensor with a new sealing gasket and torque to 60 Nm
(44.3 ft. lbs.).

WARRANTY / CLAIM INFORMATION
For vehicles within the Basic New Car Limited and / or Powertrain Warranty period, this repair may
be claimed using the following information:
LABOR DESCRIPTION

LABOR
OPERATION #

FAIL CODE

LABOR
TIME

Rear Differential Cover Gasket / Vent R&R

A372-301

KVY-34

1.2

Service Bulletin Number: 03-74-14; Date: 08/18/14

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