Toyota U660E Transmission: Aisin 6-Speed Complete Guide

BySerge Barrett

The Toyota U660E is a Aisin-sourced 6-speed automatic transmission widely used across Toyota and Lexus front-wheel-drive and all-wheel-drive platforms. Known for its smooth shifting behavior, hydraulic precision, and relatively compact design, the U660E replaced older 5-speed units and became standard equipment on several high-volume Toyota models from the mid-2000s onward. Understanding this transmission in depth — its specifications, common failure points, fluid requirements, and diagnostic codes — is essential for owners, technicians, and enthusiasts alike.

Technical Specifications of the Toyota U660E

  • Manufacturer: Aisin AW (Aisin Warner)
  • Type: 6-speed automatic, hydraulically controlled with electronic shift management
  • Drive configuration: Transverse front-wheel drive (FWD) and all-wheel drive (AWD) variants
  • Gear ratios:
    • 1st gear: 3.538
    • 2nd gear: 2.060
    • 3rd gear: 1.404
    • 4th gear: 1.000
    • 5th gear: 0.713
    • 6th gear: 0.582
    • Reverse: 3.168
  • Torque converter lockup: Available from 2nd gear and above
  • Control system: Electronically controlled via TCM (Transmission Control Module), integrated with ECM on some variants
  • Fluid capacity (total fill): Approximately 7.6–8.0 liters depending on variant
  • Fluid capacity (drain and fill service): Approximately 3.5–4.0 liters
  • Recommended fluid: Toyota ATF WS (World Standard) — lifetime spec, but service intervals recommended every 60,000–100,000 km under normal conditions
  • Weight (approx.): 85–90 kg depending on variant
  • Applications: Toyota Camry (XV40, XV50), Toyota RAV4 (third and fourth generation), Toyota Highlander, Toyota Venza, Lexus ES 350, Lexus RX 350, Toyota Avalon

Vehicle Applications by Model and Year

  • Toyota Camry XV40 (2007–2011): 2.5L and 3.5L V6 variants with U660E
  • Toyota Camry XV50 (2012–2017): 2.5L 2AR-FE and 3.5L 2GR-FE engines
  • Toyota RAV4 (2006–2012): 2.5L and 3.5L paired with U660E in FWD and AWD
  • Toyota Highlander (2008–2013): 3.5L V6 2GR-FE with U660E
  • Toyota Venza (2009–2015): 2.7L and 3.5L versions
  • Lexus ES 350 (2007–2012): 3.5L 2GR-FE engine
  • Lexus RX 350 (2007–2009): 3.5L applications prior to U760E introduction
  • Toyota Avalon (2005–2012): 3.5L V6 applications

Common Problems and Failure Modes

  • Shudder during torque converter lockup: Most frequently reported issue, typically caused by degraded ATF WS fluid or a worn torque converter clutch. Often felt as a vibration between 40–80 km/h during light throttle. Solution: fluid flush and refill with fresh Toyota ATF WS.
  • Harsh or delayed engagement from Park/Neutral to Drive/Reverse: Often fluid related, but can also indicate worn solenoids (particularly S1 or S2 shift solenoids) or internal valve body wear.
  • Slipping between 3rd and 4th gear: Associated with worn C2 clutch pack or low line pressure due to faulty pressure control solenoid (SLT solenoid).
  • Fluid leaks from output shaft seal or pan gasket: Common on higher-mileage units. The U660E uses a reusable pan gasket on some variants; replacement with OEM or quality aftermarket seal is recommended.
  • Overheating: Insufficient ATF cooling, particularly in towing applications. The factory cooler may be undersized for heavy-duty use.
  • Valve body sticking or solenoid failure: SL1, SL2, SLT, SLU solenoids are prone to wear after 150,000+ km. Manifests as erratic shifting, delayed shifts, or limp mode activation.

Transmission Solenoids

  • S1 (Shift Solenoid 1): Controls 1st/2nd gear engagement
  • S2 (Shift Solenoid 2): Controls 3rd/4th gear engagement
  • SL1 (Linear Solenoid 1): Clutch C1 apply pressure regulation
  • SL2 (Linear Solenoid 2): Clutch C2 apply pressure regulation
  • SLT (Linear Solenoid T): Line pressure control — critical for overall shift quality
  • SLU (Linear Solenoid U): Torque converter lockup clutch control

OBD-II Diagnostic Trouble Codes (DTCs) Specific to U660E

  • P0710 — Transmission Fluid Temperature Sensor Circuit Malfunction: Causes include faulty TFT sensor, wiring harness damage, or poor connector contact
  • P0711 — TFT Sensor Performance: Sensor reading not changing as expected, often indicates sensor failure or intermittent electrical fault
  • P0750 — Shift Solenoid ‘A’ (S1) Malfunction: Causes include solenoid failure, valve body wear, or TCM fault
  • P0755 — Shift Solenoid ‘B’ (S2) Malfunction: Same causes as P0750, affects upper gear ranges
  • P0770 — Shift Solenoid ‘E’ (SLU) Malfunction: Torque converter lockup issues, shudder, reduced fuel economy
  • P0776 — Pressure Control Solenoid ‘B’ (SL2) Performance/Stuck Off: Slipping in specific gear ranges, often 3rd/4th
  • P0796 — Pressure Control Solenoid ‘C’ (SL3) Performance/Stuck Off: Affects clutch application in mid-range gears
  • P0973 — Shift Solenoid ‘A’ Control Circuit Low: Electrical fault in S1 wiring or solenoid coil
  • P2714 — Pressure Control Solenoid ‘D’ (SLT) Performance/Stuck Off: Line pressure fault, hard shifts or limp mode
  • P2716 — Pressure Control Solenoid ‘D’ Electrical: Open or short circuit in SLT solenoid circuit
  • P0741 — Torque Converter Clutch Circuit Performance/Stuck Off: TCC not locking, poor fuel economy, shudder at highway speeds
  • P0746 — Pressure Control Solenoid ‘A’ (SL1) Performance/Stuck Off: C1 clutch pressure fault, slipping in 1st/2nd

Fluid Service Procedure

  • Drain plug location: Bottom of transmission pan; 24mm bolt with crush washer
  • Pan removal: 10mm bolts (typically 16–18 bolts); internal filter should be replaced during full service
  • Filter type: Internal mesh/felt filter, part of valve body assembly; replaceable unit available separately
  • Fluid specification: Toyota ATF WS only — do not use Dexron VI or generic ATF without WS specification
  • Refill quantity after drain and fill: 3.5–4.0 liters
  • Full flush quantity: 7.6–8.2 liters total system capacity
  • Service interval recommendation: Every 60,000 km under normal use; every 40,000 km in towing or severe duty cycles
  • Fluid check procedure: Requires vehicle at operating temperature (fluid temp 65–75°C), level checked via overflow bolt on some variants or dipstick on earlier models

Rebuild and Overhaul Notes

  • Clutch packs: C1, C2, C3, B1, B2, B3 — all friction discs must be measured against OEM thickness tolerances during rebuild
  • Thrust bearings and washers: Full bearing kit recommended during overhaul to address cumulative wear
  • Valve body reconditioning: Solenoids should be tested with a multimeter; S1/S2 resistance spec approximately 11–15 ohms; SL solenoids approximately 5–6 ohms
  • Torque converter: Replacement strongly recommended if shudder persists after fluid change; remanufactured units widely available
  • TCM adaptation reset: After any significant repair or fluid service, perform a TCM idle relearn and transmission adaptation reset using a Toyota-compatible scanner (Techstream software)

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