This document describes the functions and major components of the Subaru 4EAT transmission, as well as the electronic control system and hydraulic control system.
The Subaru 4EAT is a four-speed, microprocessor-controlled automatic transmission that was first introduced in 1987.5 Subaru models. It uses a lock-up torque converter that locks in all forward gears except 1st and has been offered in front-wheel-drive and Full Time AWD configurations. The document describes its major components, double planetary gear train, transfer clutch assembly for AWD, hydraulic band servo operation and power flow through the forward gears.
It also explains the Transmission Control Unit inputs and outputs, the electronic control system, the self-diagnostic system with fail-safe function, and troubleshooting and adjustment topics. Service information is presented as an overview, with references to the applicable Subaru service manual for model-specific details.
| Transmission type | 4 speed, microprocessor-controlled |
|---|---|
| Torque converter lock-up | All forward gears except 1st |
| Drive configurations | FWD or Full Time AWD |
| Gear train | Double planetary gear set |
| First gear output ratio | 2.785:1 |
| Second gear output ratio | 1.545:1 |
| Third gear output ratio | 1:1 |
| Fourth gear output ratio | 0.694:1 |
| Legacy shift quadrant | Seven position: P-R-N-D-3-2-1 |
The Subaru 4EAT is a 4 speed, microprocessor-controlled automatic transmission introduced in 1987.5 Subaru models.
It locks up in all forward gears except 1st.
It has been offered in FWD or Full Time AWD configurations.
The TCU controls shifting and line pressure, along with the lock-up torque converter and the MPT clutch.