Toyota Hilux Surf: A340F Overdrive Solenoid Failure & 4th Gear Slip

The A340F 4-speed automatic transmission fitted to VZN185 HiLux Surf automatic variants is known to develop overdrive solenoid (S4 solenoid) failure on high-mileage examples. The overdrive solenoid controls hydraulic pressure to the overdrive clutch pack. When it fails electrically or the solenoid bore wears, the transmission slips on engagement of 4th gear (overdrive) causing engine RPM to flare under load at highway speeds. The OD OFF button illumination may flash or behave erratically. If driven in this condition, friction material in the overdrive clutch pack wears rapidly and contaminates transmission fluid, escalating to a full transmission rebuild. Early solenoid-only repair is significantly cheaper than the rebuild cost incurred by delayed diagnosis.

• Engine RPM flares at highway speed when transmission attempts to engage 4th gear
• OD OFF dashboard light flashing or illuminating spontaneously
• Transmission hunting between 3rd and 4th gear on level road at cruise speed
• Harsh or delayed upshift into overdrive
• Transmission slips under acceleration above 90 km/h
• Check engine light with P0755 or related solenoid circuit fault codes

1. 1

   Test drive at highway speeds and confirm smooth positive engagement of all four forward gears including overdrive under light and moderate acceleration.

2. 2

   Pull transmission fluid dipstick and check for dark brown discolouration or burnt smell indicating clutch material contamination.

3. 3

   Confirm OD OFF switch on dash operates correctly.

4. 4

   If a workshop inspection is possible: Scan for OBD fault codes in transmission module specifically P0750-P0760 range covering A340F solenoid circuits.

Parts involved: Clutch.

$350 to $4,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the OD OFF light ever flashed or the transmission been serviced for slipping?”
• “Does the transmission shift smoothly into all four gears including overdrive at highway speed?”
• “Has any transmission repair or rebuild been carried out, and are workshop records available?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.