Toyota/Lexus U140E suddenly loses reverse

Toyota/Lexus U140E suddenly loses reverse

The complaint

A 2002 Lexus RX300 with 3.0-liter engine and the A140F AWD Transmission developed a sudden issue: a loss of reverse and no ability to upshift out of first gear. Fault code P0750 “Shift Solenoid SL1 Performance Malfunction” was set.

Scan tool data did indicate that the transmission range sensor was operating properly, and a shift into second was commanded even though the transmission remained in first gear. The transmission case connector was disconnected, resulting in the same no-reverse condition and being stuck in first gear.

The pan was dropped and an air check procedure was performed with good results. With the valve body removed and inspected no problems were found; however, the SL1 Solenoid was replaced. With the valve body installed back into the vehicle, the same complaints remained. At this time, the transmission was removed for inspection.

The cause

The direct clutch sun gear had broken away from the clutch hub, as seen in the image above.

The correction

With the direct clutch sun gear hub replaced, the transmission returned to normal operation.

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