Controlling the Aisin A340, A341 and A343 Transmissions with the COMPUSHIFT Sport

History of the Aisin A340 Transmission

The Aisin A340, released in 1985, is a 4-speed electronically controlled automatic transmission designed by Aisin Warner. The biggest manufacturer of automatic transmissions in the world, headquartered in Japan.

The A340 was initially released in Toyota vehicles (the largest shareholder of Aisin Warner), before soon getting featured in other vehicles made by Lexus and Kia.

Few years after the A340, the A341 and A343 transmissions were launched. Their design was heavily influenced by the original A340, but they were slightly modified and improved internally to suit the vehicles they were built for better.

The A340, A341 and A343 range of transmissions were featured in various different types of pickups, sporty sedans and SUVs. It was in production for over 20 years into the early 2000’s before being subsequently phased out to make way for newer 5 and 6-speed transmissions. Their reliability, versatility and performance made them a very popular series of automatic transmissions all across the world.

Specifications of the A340, A341 and A343 Transmissions

The A340 series of transmissions came in various variations over the years built specifically for different vehicles and purposes. They are generally rated to be medium torque transmissions. However, with the appropriate modifications they can easily handle a lot more horsepower and torque.

Their name codes reveal in more detail the features of the transmissions:

A – Refers to Aisin Automatic

3 – Refers to the generation of the transmission.

4 – 4 Forward Gears.

0 – Identifies the variant of the transmission

There’s also an additional letter at the end of the transmission to identify the unique model. For instance, in the A340H, A340E, A341E or A341F, the letters refer to the following:

E - refers to the electronically controlled 2-wheel drive version

F - refers to the 4-wheel drive version

H - refers to the version for AWD transverse mounted engines

S - means it can be controlled by a tip-tronic gear shift control

The A340E in stock form can handle up to 320 horsepower and around 300-350 lb-ft of input torque.

The A341E builds upon the A340E and is used on turbocharged vehicles as it’s capable of handling more torque and horsepower. It also has an additional shift control solenoid that helps control shift feel by controlling the engagement speed, this helps reduce the jolting shocks felt from gear shifts.

Finally, the A343E is basically an upgraded A340E transmission. It has more in common with the A340E than the A341E, as the A341E has a different gearing ratio (see below). All the transmissions have almost the same control mechanism, with a couple of minor differences between its many variations

The Jeep AW4 and Other Variants

Not everyone is aware that the AW4 used in various Jeep vehicles is actually a rebadged A340. In fact, the A340 comes in many variations with some having variable torque converter clutch and accumulator pressure controls for additional tuning flexibility. Some A340's variations have internal temperature sensors, and others do not.  For those A340's without an internal temperature sensor, COMPUSHIFT A340 kits include an external temperature sensor that can be fitted to cooler lines.

One of the more unusual variations is the A340 30-40LS, which was paired with the 2JZ-GTE twin-turbo engine on the Toyota Aristo and other Japanese domestic market (JDM) vehicles. This heavy duty version has two additional shift solenoids that allow paddle shifting with engine braking in all gears (also supported by the COMPUSHIFT). Power on this transmission is limited to about 500HP on the stock internals, but can be built to handle significantly more. The A340 0-40LS can be easily identified because the bell housing has "J3" cast into the upper surface, and is larger diameter to accept the larger torque converter and special flex plate. The main case is similar to the common A340E but not interchangeable.

If you are looking to control an A340 using a COMPUSHIFT stand alone transmission controller we can help you get the right harness for your variant of A340. Just head over to our Configurator which covers the A340 and AW4 and our short survey will ensure you get exactly the kit you need.

Gear Ratios of the A340E, A341E, and A343E Transmissions

A340E

1st 2nd 3rd 4th R
2.804 1.531 1.00 0.705 2.393

A341E

1st 2nd 3rd 4th R
2.531 1.531 1.00 0.705 1.880

A343E

1st 2nd 3rd 4th R
2.804 1.530 1.00 0.753 2.393

The A340E and A343E transmissions have almost the same gearing ratio, with the exception of 4th gear. The A341E is mainly used in sedan cars, so it has a taller gearing ratio allowing it to reach higher speeds for a given rpm.

Strengths of the A340 Transmissions

The A340 transmissions were very popular for their ability to handle a lot of torque and horsepower. Whether that be the torque from a Toyota Tundra’s V8 or the horsepower of a Supra’s twin-turbo 2JZ-GTE engine, the transmissions worked excellently in a whole host of different conditions and vehicles. With the right modifications, the transmissions were able to handle more than 500hp.

The A340 models are all electronically controlled via the use of solenoids. Compared to the A43D which was released few years prior, the A43D is hydraulically controlled with a governor. Hence, adjusting the shift strategy and diagnosing issues is a lot more time consuming and complicated compared to the A340 transmissions. Early versions of the A340 range of transmissions ran a pressure control cable that was later replaced with a pressure control solenoid. Both variants are still considered to be full electronically controlled as they run shift solenoids.

The advantages of having an electronically controlled transmission are numerous. In terms of driving, you get improved drivability and fuel economy through a highly accurate shift control mechanism, which monitors throttle position, engine revs, vehicle speed, water temperature and brake application.

All models of the A340 and its variants have a torque converter clutch. When locked up, it provides a direct drive from the engine, eliminating slippage in the torque converter, which improves fuel economy at cruising speeds.


Weaknesses of the A340 Transmissions

While most of the A340, A341 and A343 transmissions are highly reliable, it is usually electronical issues related to the solenoids that affect the transmission’s operation.

In some of the early models, issues concerning the valve body caused hard shifting and engagement issues. This got resolved to some extent in later models. The 2nd gear sprag assembly is also another well-known weak point of the stock transmissions. This and the stock torque converter clutch are often rebuilt and upgraded to handle more torque.

One of the most important considerations with this transmission is proper maintenance. Owners need to change the transmission fluid and filter at regular intervals, otherwise debris which accumulates over time can led to shifting issues and a noisier ride.

Problems with the transmission can also stem from rough driving. Some of this can be caused by the driver, however on roads where lots of shifts are needed, the transmission’s

temperature can get too hot, and this can lead to shifting issues over time. If needed, the cooling system should be upgraded to dissipate excess heat.


Popular Custom Vehicles that use the A340, A341 and A343 Transmissions

It is common to find owners substituting their transmissions with different variants of the A340E, as long as the type of vehicle is similar. One needs to consider the engine it’s being linked to, as well as the type of transfer case if using it in an AWD vehicle. Some transmissions such as the A340H are not interchangeable due to having a fixed transfer case.

In the custom car scene, these transmissions are commonly found on customized JDM (Japanese Domestic Market) vehicles. One can find the A340E in Toyota Supras and RWD Tundras. The A341E is commonly bolted onto the highly renowned Toyota 1UZ engine. The A340F and A343F can also be found on some of Toyota’s toughest vehicles such as the 4WD Landcruiser, Prado, Hilux and Lexus LX450.

Outside Toyota, the A340E and its variants can be found on Lexus, Kia, Isuzu, Mitsubishi and Volvo vehicles too.


A First-Gen Toyota Tundra which had models that featured the A340E


A 2nd Gen Lexus GS300 which used either a A340 (30-40LS) or A341E transmission


A 100 series Toyota Landcruiser which featured the A343F Transmission. Also known as the Lexus LX470.

Controlling the A340, A341 and A343 with a COMPUSHIFT transmission controller

If you have a vehicle with one of the A340 transmissions, or are looking at using it in a custom vehicle build, whether that be for street or off-road use. Having a well-tuned transmission shift strategy and control over its operation can significantly improve your driving experience.

A reliable transmission controller like the COMPUSHIFT Sport can do all this and more. It’s tested and proven to work seamlessly with all variants of the A340E regardless of your engine preference.

One of the biggest advantages that the COMPUSHIFT Sport transmission controller has, is that it can be connected to a smart phone via Bluetooth. The shift strategy, torque converter clutch lockup, and transmission diagnostics can be viewed and adjusted on the go via the accompanying app.

To use the Compushift Sport, one will need a compatible mechanical shifter, the correct speed and throttle sensors as well as a compatible wiring harness. This will all depend on the type of engine and engine control unit being used. To find out exactly what you need to control your A340, A341 or A343 transmission, head over to our configuration tool.

To get pricing for the COMPUSHIFT transmission controller click the below link to complete a quick questionnaire:

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