Toyota vehicles are known for their reliability, the Aisin designed 4 speed Automatic found in the Toyota Hilux and Prado is a proven unit that has been slowly developed from the late 1980s. The A343F which is a 4WD version fitted from 2005 to 2015 can take quite a beating but it has one issue that can bring the whole house of cards tumbling down.
Keeping its cool while under under pressure
The automatic transmission uses a small bodied torque converter to generate heat and put the factory cooling system under stress. Once the automatic transmission fluid is under stress the standard cooling system can’t maintain the correct fluid temperature, with the increased ATF temperature the converter can be overstressed to the point of failing the lock-up clutch plate and the internal bearings. The debris will then make its way through the pump and into the rest of the transmission causing a complete automatic transmission failure.
Navigating the debris field
Most often by the time you notice something is wrong, it’s too late and the metal and clutch debris has already done its damage. The three main components that are affected are the torque converter, transmission pump assembly and the valve body assembly.
The Torque converter can be pushed to the point where the core will be destroyed and it can’t be reconditioned. The Pump will also be damaged to the point the gear clearance will be excessive or the converter neck bush will tear itself apart requiring a complete pump replacement. The valve body will get full of debris and chew up the valve bores causing cross leaks that may not be able to be reamed and new oversized valves fitted.
Get it right the first time
Our rebuild procedure for this transmission has been a continuous development since 1998 which has allowed us to increase the reliability of a high kilometer unit. With the addition of an extra external automatic transmission oil cooler and the addition of a transmission service added to the vehicle service schedule. This makes the A343F unit one of the more reliable automatic transmissions fitted to a dual cab ute or SUV wagon.
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