Humming / High Pitch Sound From Drive Line – 2017-2021 Subaru

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Bulletin Number: 03-87-21; Date: 01/14/22 Page 1 of 4 SERVICE BULLETIN 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. 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. NUMBER: 03-87-21 DATE: 01/14/22 APPLICABILITY: 2018-21MY Legacy & Outback 2017-21MY Impreza 2018-21MY Crosstrek 2019-21MY Forester SUBJECT: Humming / High Pitch Sound From Drive Line INTRODUCTION: This bulletin provides a repair procedure for R152 type rear differentials. In some very rare cases, a customer may experience a humming / high pitch sound coming from the undercarriage while driving. This can be caused by worn differential gear surfaces resulting from hard usage of the vehicle such as extreme weather conditions, severe road conditions, and / or steep incline driving. A higher viscosity (thicker) gear oil has been introduced to provide additional protection against premature gear surface wear under these unusual driving conditions. PRODUCTION CHANGE INFORMATION: The higher viscosity fluid (75W-90) has been incorporated into production per the table below. Model Starting VIN Legacy M3019244 Outback M3197842 Impreza 4-Door M3606662 Impreza 5-Door M3714901 Crosstrek MH321913 Forester MH492693 ATTENTION: GENERAL MANAGER q PARTS MANAGER q CLAIMS PERSONNEL q SERVICE MANAGER q IMPORTANT – All Service Personnel Should Read and Initial in the boxes provided, right. ©2021 Subaru of America, Inc. All rights reserved. Bulletin Number: 03-87-21; Date: 01/14/22 Page 2 of 4 Continued… PART INFORMATION: REMINDER: Always order the most up-to-date replacement parts based on the specific VIN being repaired. Part Description Part # Type R152 I.D. Numbers Differential Model # Reduction Ratios DIFFERENTIAL CARRIER ASSEMBLY 38300AC370 42 VB1AAB 3.700(37/10) 38300AC380 43 VB1BAA 3.900(39/10) 38300AC390 44 VB1CAA 4.111(37/9) 38300AC440 E1 VB1AAC 3.700(37/10) SELF-LOCKING NUT 023512000 – Part Description SOA Item # Description Package Size Warranty Part # High Performance 75W90 SOA427V1700 Gear Oil Case of 12/1 qt. SOA635301 per qt. SOA427V1710 16 Gallon Keg NOTE: The Differential Mount Locking Nuts p.n. 023512000 are one-time use parts. Refer to the applicable Service Manual and Electronic Parts Catalog (EPC) for the quantity requirements. SERVICE PROCEDURE / INFORMATION: REMINDERS: • Customer satisfaction and retention starts with performing quality repairs. • Please read all the Steps outlined below before proceeding with any work. Identification: Confirm the source of the sound is the rear differential and not from the wheel bearings and drive shafts before proceeding. It is important to identify the rear differential type to verify applicability before proceeding with any service procedures. The information below will outline how to identify the differential type. STEP 1) Locate the identification number located on the rear differential. (1) LABEL (2) REAR DIFFERENTIAL SERIAL NUMBER (3) REAR DIFFERENTIAL IDENTIFICATION NUMBER EXAMPLE: EXAMPLE: REAR DIFFERENTIAL I.D. #44 SHOWN Bulletin Number: 03-87-21; Date: 01/14/22 Page 3 of 4 Continued… STEP 2) Compare the identification number with the part information chart provided on Page #1. Does the identification number match the part information shown? The rear differential is a R152 type. Continue to STEP 3. The rear differential is NOT a R152 type. Continue diagnosis as per the applicable Subaru Service Manual: Driveline/Axle > Symptoms and causes > INSPECTION. STEP 3) Refer to the applicable Service Manual and review: General Description > Repair Contents > Action required before & after Battery Disconnect. Additionally, record any stored seat position(s) before proceeding. Relearn any seat position memory after work is complete. If the power rear gate (PRG) height has been customized, that position must also be noted and relearned. STEP 4) IMPORTANT: The new rear differential MUST be filled with the new 75W90 gear oil. The service procedure for rear differential replacement remains unchanged. Always refer to the applicable Service Manual and review the full requirements of the repair being performed. The Service Manual procedures contain information critical to performing an effective repair the first time, every time. This includes but is not limited to important SAFETY precautions, proper inspection criteria, necessary special tools, required processes and related one-time-use parts needed for a complete and lasting repair. Refer to the applicable Subaru Service Manual: Driveline/Axle > DIFFERENTIALS > Rear Differential. IMPORTANT NOTES: • The Service Manual uses a black star () in the component breakdown illustrations to indicate one-time use parts. For example, T1 and T2 are self-locking nuts (023512000) and are one-time use only. See the image to the right. • Whenever reconnecting the ground cable terminal to the battery sensor, torque to 7.5Nm (5.5ft.-lbs. or 66 inch-lbs.) while supporting the sensor with the other hand as outlined in the applicable Service Manual under: STARTING/CHARGING SYSTSEMS > Battery Sensor. YES: NO: Bulletin Number: 03-87-21; Date: 01/14/22 Page 4 of 4 WARRANTY / CLAIM INFORMATION: For vehicles within the Basic New Car Limited, Powertrain, an active Subaru Added Security Powertrain, Classic or Gold plan, this repair may be submitted using the following claim information: Model Labor Description Labor Operation # Labor Time Fail Code Legacy/Outback REAR DIFFERENTIAL ASSEMBLY R&R B372-001 0.8 KCA25 DIFFERENTIAL NOISE TESTING & DIAGNOSIS C363-001 0.3 Impreza/Crosstrek REAR DIFFERENTIAL ASSEMBLY R&R B372-001 1.0 DIFFERENTIAL NOISE TESTING & DIAGNOSIS C363-001 0.3 Forester REAR DIFFERENTIAL ASSEMBLY R&R B372-001 0.8 DIFFERENTIAL NOISE TESTING & DIAGNOSIS C363-001 0.3 IMPORTANT REMINDERS: • SOA strongly discourages the printing and/or local storage of service information as previously released information and electronic publications may be updated at any time. • Always check for any open recalls or campaigns anytime a vehicle is in for servicing. • Always refer to STIS for the latest service information before performing any repairs.

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