Drive Chain May Break Causing Loss Of Drive Power

In December 2018, Subaru of America, Inc. (Subaru) received a report about one of their vehicles in the US market that experienced an inability to shift into drive. Subaru collected the parts for further investigation and found that the chain guide had been damaged. The cause of the broken chain guide could not be determined so Subaru opened an investigation with the supplier.

By August 2020, Subaru had received 12 technical reports from the U.S. market with claims that included not being able to shift into “Drive” or “Park”, the inability to start the engine, and contaminants in the transmission fluid pan. As a result of the investigation, an updated transmission control unit (TCU) control program was implemented on the manufacturing line and Subaru continued to monitor the field data. During this period, Subaru received 11 more technical reports, one of which the drive chain slipped while the vehicle was in motion.

Subaru is aware of 23 technical reports in the U.S. market and has decided to conduct a safety recall.

According to the defect report, “Due to an improper program, if the shift select was moved to drive or reverse (D or R) immediately after the engine was started, the independent secondary pressure control program may allow the Forward / Reverse (F/R) clutch to begin engagement before enough secondary clamping pressure has been applied to the drive chain. Insufficient clamping pressure may cause the drive chain to slip, the chain guide could break apart and the fragments could inhibit the shift select mechanism. In addition, over time, if the vehicle continues operation with the drive chain slipping, the drive chain could eventually break.”

Dealers will reprogram the TCU, inspect TCU data for chain slip, and visually inspect the chain and guide. If evidence of chain slippage or damage is found, the transmission will be replaced. This recall includes all vehicles previously recalled under 19V-855. Vehicles previously recalled under 19V-855 will need to have the new remedy performed for this recall once available. Subaru's number for this recall is WRK-21 and the NHTSA campaign number is 21V-995.