History of the Toyota A750
Aisin Warner, the largest global manufacturer of automatic transmissions, designed and manufactured a 5 speed full electronic automatic transmission code named TB-50LS. Vehicles manufactured by companies such as Toyota, Mitsubishi, Isuzu, and Suzuki have all featured this 5 speed automatic transmission from Aisin Warner.
One of those manufacturers, Toyota, used this transmission extensively throughout the 2000’s and early 2010’s. Toyota provides their own model code of A750, with variants of 2WD coded as A750E and 4WD coded as A750F.
First featured in the late 2002 Toyota 4-Runner and Land Cruiser, the A750 was predominately used in trucks and SUVs such as the Tundra, FJ Cruiser, Prado, Hilux and Fortuner. Also making the long list is the Lexus LX470 and GX470. Most were to use the 4WD variant of the A750, the A750F.
There were also some 2WD variants used in the Toyota 4-Runner, Tacoma V6, FJ Cruiser, Sequoia, and Hilux.
Considered by many professionals to be one of the most reliable transmissions built by Aisin, the A750 manufacturing cycle lasted well over 10 years. However as the requirement for reduced emissions and increased fuel economy continued to be top priority, the A750 was slowly replaced with 6-speed and 8-speed automatic transmissions. In some cases, gaining a very little improvement over the A750 figures.
Specifications of the A750
The A750 is considered to be a medium torque capacity transmission and it is rated for use with engines that produce less than 550 Nm of torque output at the crank and with a displacement up to 4.5L (275in³). That being said, because the COMPUSHIFT system has the ability to raise / calibrate pressures as required, we have improved the torque capacity up to 650Nm.
The A750 weighs in at about 187 lbs. (85 kg), and its operation is electronically controlled by solenoids in the valve body.
Each A750 transmission is built slightly differently depending on the engine and vehicle it’s being used in. For example, the Toyota Land Cruiser 4.2L 6 Cylinder Turbo Diesel and the Hilux 3.0L 4 Cylinder Turbo Diesel both use the A750F Transmission but require different torque converters due the different torque output and vehicle weight. Even though the two transmissions operate in the same manner, the two are not interchangeable.
Some A750s, especially those sold in cold weather countries have an automatic transmission fluid (ATF) warmer, which uses the engine’s heat to warm the transmission oil. This helps get the transmission up to the ideal working temperature, helping reduce friction losses.
Being an electronic transmission, the control of the transmission is vitally important. Compared to 4 speed automatic transmissions, the 5 speed A750 transmission requires a considerable amount of precision from its control system in order to achieve reliable and smooth operation.
In the majority of 4 speed automatic transmissions there is only the need for a single change to the shift solenoids to achieve the desired gear. In the A750 transmission, each shift requires a sequence of shift solenoid positions to make the gear changes smooth and reliable.
The A750, along with most modern transmissions, also has a solenoid activated Torque Converter Clutch (TCC). The TCC can be locked up to help drop engine rpm on the highway. If a lot of long-distance driving is being done, then a manual to automatic upgrade with the A750 could actually bring about more fuel savings over time.
Gear Ratios of A750
| 1st | 2nd | 3rd | 4th | 5th | R |
| 3.350:1 | 2.042:1 | 1.40:1 | 1:1 | 0.716:1 | 3.22:1 |
Strengths of the A750
The biggest strength of the A750 is its reliability if serviced properly and used sensibly. It has proven to be very capable of working without problems in hot temperatures in regions such as the Middle East and Australia, as well as in the freezing cold in North America and Europe.
While each vehicle configuration has its own set of strengths and weaknesses, variants found in the Toyota LandCruiser and Lexus LX470 are considered to be one of the more reliable versions. With increased diameter shafts to handle the added weight of the larger SUVs and extremely well built torque converters, these variants are commonly used for swap outs into custom vehicles.
Common Problems / Weaknesses with the A750
The A750 is customized for use in different makes and configurations like in 4x4s and Rear-Wheel Drive vehicles (RWDs). Common problems and weaknesses on one model’s A750 might be very rare on another model’s A750.
Therefore, if you were to ask what are the common problems or weaknesses, the answer would simply be – it varies! However, there are one or two issues that have become common amongst the many variations.
Main Forward Clutch Failure
Inside the A750 transmission are 7 clutches in total, with an 8th clutch inside the torque converter. However, there is one clutch that has the smallest friction surface area that during one particular shift takes the entire load of the engine. This clutch is the main forward clutch or C1. The shift in question is the 5-4 kickdown.
With modern engines producing more and more power, the thirst for more power in older vehicles becomes greater. This is where the C1 clutch failure shows itself. Due to larger turbochargers, superchargers or high flow injectors, the increased torque available at lower throttle positions means the amount of torque delivered to the C1 clutch becomes too great and slipping starts to happen.
Enough slipping of this clutch can result in the clutch welding itself on permanently. If this happens, the resulting fault reported by the driver will be the absence of 5th gear. This is because the C1 clutch needs to disengage for the 4-5 upshift.
The only way to fix this is through a transmission overhaul, and a reduction in engine torque to a more suitable level. That being said, there has been many cases where an engine upgrade chip has caused failure due to incorrect calibration. If your engine runs any form of upgrades it is imperative to monitor transmission pressures.
Rough Downshifting
Rough downshifting appears mechanical in nature but quite often is a result of electronics failing, presenting itself as a rough downshift when coasting to a stop. The electronics in this case are the electromechanical solenoids inside the transmission. These solenoids turn the electrical signals from the Transmission Control Module (TCM) into mechanical actuations which in turn controls the pressure inside the transmission clutches.
In the case of the rough downshifting, when the Main Pressure Solenoid, referred to as the Line Pressure or SLT solenoid, fails to move correctly, there is insufficient pressure to perform the downshift. When the TCM detects that the downshift has not completed, the TCM will start ramping up pressure to force the shift to happen. The resulting feeling of the clutch finally engaging can feel so harsh that you may think you have hit the world’s largest pothole.
Popular Custom Vehicles that use the A750
You’re not limited to only using the A750 in a vehicle that originally came with one. There have been A750s added to SUVs from other models, but more commonly, older Toyota vehicles with a manual gearbox such as the 70 Series and 80 Series Land Cruisers have their manual gearboxes swapped out for the A750 automatic transmission.
Since older manual vehicles lack the electrical control systems to manage and control an automatic transmission, you’ll need a transmission controller such as the COMPUSHIFT Pro along with the appropriate wiring loom to integrate the automatic transmission with the engine and vehicle. On top of that, you will have to take into consideration the new gear ratios after the conversion and whether you’d need to make any changes to the final drive ratio.
A 4WD Toyota Hilux
A 100 series Toyota Land Cruiser
A750 Transmission Control with the COMPUSHIFT
If you’ve decided to upgrade your manual gearbox to a highly refined 5 speed automatic transmission such as the Toyota A750, the COMPUSHIFT Pro transmission controller is the perfect solution to provide a customizable transmission controller to suit the many variations of custom vehicles that exist in the world today.
With nothing more than a smartphone, which everyone has these days, you can completely configure the COMPUSHIFT Pro transmission controller for your vehicle setup via a free to download App which communicates to the COMPUSHIFT Module wirelessly via Bluetooth.
While the A750E and the A750F both use the same main harness, there are some options when it comes to the shifter used inside the vehicle. The two main shifter configurations are Gate shift and Tip-Tronic shift.
Gate shift is determined by the physical location of each gear position on the shifter, whereas the Tip-Tronic versions have physical positions for Park, Reverse, Neutral and Drive positions.
The COMPUSHIFT can work with the Tip-Tronic shifters found in the Toyota Prado and Tundra. There are also options for using the Gate Shifters from the LandCruiser and Hilux. In some cases, there even exists the ability to modify a transmission from gate shift to tip-tronic for the best of both worlds, however this requires upgrading to a Nomad valve body from Wholesale Automatic Transmission to work correctly.
One item to note is that the Manual Lever Position Switch (MLPS) from early model A750 transmissions is not compatible with the COMPUSHIFT Loom due to the availability of the connectors and terminals. The MLPS that was available on the later models is the one the COMPUSHIFT supports. If you have one of the early model MLPS then you may need to upgrade your transmission to the later model MLPS so that the COMPUSHIFT will work correctly.
To get details on the COMPUSHIFT A750 transmission controller click the below link:
