Subaru TZ1B4Z 4-Speed Automatic Transaxle (Turbo) · Subaru · Expert rebuild service since 1987. Lifetime warranty. Free diagnostic.
2002–2007 Subaru Impreza WRX (EJ20T/EJ25T turbo), 2004–2009 Subaru Forester XT (turbo), 2005–2009 Subaru Legacy GT/Outback XT (turbo)
| Configuration | 4-speed automatic AWD transaxle (turbo-rated) |
|---|---|
| Gear Ratios | 1st 2.78:1 · 2nd 1.55:1 · 3rd 1.00:1 · 4th 0.69:1 · Rev 2.27:1 |
| Fluid Type | Subaru ATF HP or Idemitsu ATF |
| Fluid Capacity | 7.5 qts total, 3.4 qts service refill |
EJ20T/EJ25T turbocharged torque is significantly higher than the NA counterpart. Clutch packs in the TZ1B4Z wear much faster, especially in enthusiast-driven WRX applications.
Symptoms: Slip under hard acceleration, RPM flare, DTC P0732–P0737, burnt ATF smell
TCC shudder from degraded ATF is more aggressive in turbo applications due to higher heat loads.
Symptoms: Highway vibration, DTC P0740, shudder worse after extended WOT runs
Solenoid body failure from heat cycling under turbo boost loads causes shift quality issues.
Symptoms: Harsh shifts, DTC codes, limp mode
TZ1B4Z rebuild replaces all clutch packs (upgraded for turbo torque), solenoid body, torque converter, and all seals. Subaru ATF HP used. Turbo-specific upgraded friction packs installed.
Subaru ATF HP every 25,000 miles for turbocharged applications — shorter than non-turbo interval. WRX and Forester XT owners who drive enthusiastically should consider 20,000-mile intervals.
The TZ1B4Z is the turbocharged variant with upgraded clutch capacity for EJ20T/EJ25T applications. The TZ1A4Z is for naturally aspirated models.
Impreza WRX, Forester XT, Legacy GT/Outback XT with turbo engine and automatic transmission.
Less so than the manual — the TZ1B4Z was not designed for WOT turbo launches. Diligent ATF HP service and avoiding aggressive driving extend life significantly.
A full rebuild ranges $1,700–$2,200 at Chicago Transmission.
Subaru ATF HP or Idemitsu ATF — every 25,000 miles for turbocharged applications.
Free diagnostic, written estimate, lifetime warranty. Chicago's TZ1B4Z rebuild specialists since 1987.
