Yesterday I turned my attention to the transmissions. As far as I know I have two types of transmissions. I took an A342E out of the Lexus LS400 (1995) with the 1UZ engine and bought an A343F from a UZJ100 that had a 2UZ engine. I want to use the 1UZ ECU to shift the A343F out of the UZJ100 but there are some challenges.
In the Lexus LS400 (1UZ & A342E combo) the following valves are controlled by the ECU:
- S1 Solenoid valve for shifting gears;
- S2 Solenoid valve for shifting gears;
- SL Solenoid for locking torque converter;
- Accumulator piston assembly, this solenoid "controls" the accumulator (back pressure?) for smooth shifting.
There was also a mechanical valve controlled by a cable. This cable is connected to the throttle and mechanically controls Line Pressure in the transmission.
In the Land Cruiser UZJ100 (2UZ & A343F combo) the following valves are controlled by the ECU:
- S1 Solenoid valve for shifting gears;
- S2 Solenoid valve for shifting gears;
- SL Solenoid for locking torque converter;
- SLT Line pressure solenoid for controlling line pressure.
There is no mechanical cable action here. As far as I know the more current flows through the line pressure solenoid valve the lower the line pressure is. It might be the other way round, I based this on the following chart:
So, how will I connect the A343F to the 1UZ ECU?
- S1 will go to S1 & S2 to S2, that's the simple part.
- the SL will connect to SL. The solenoid valve looks different and I read somewhere that the solenoid valve is driven by PWM lower that 100%. I'll have to look that up or measure it when everything is installed in the Cruiser.
- The wires from the ECU to the Accumulator piston assembly will be left loose since the A343F does not have this solenoid valve. The ECU might throw a code, then I will have to connect a resistor to these wires to "simulate" the valve. Does anyone know how the A343F handles this accumulator (back)pressure?
Then the hard part comes. The A342E had a throttle cable that regulated the line pressure. More throttle means more line pressure. I want to drive the Line Pressure solenoid the same way.
I'll install a TPS (throttle position sensor) and read the throttle position with a microcontroller. Then the microcontroller will drive the Line pressure solenoid valve with 100-30% (of something like that) PWM. I can control the line pressure proportional to throttle position.
This is just the plan, if someone sees something wrong with this or has any tips please let me know.
I'll post some pics of the Solenoid valves of both transmission and the pinout of the solenoid connectors.
Let's start with the A342E that came out of the Lexus LS400. In the picture below you can see the solenoids. I added the function of the solenoid & the wire colour:
And here is the pinout of the solenoid valve connector:
The A343F looks very different, you can see the valve body below. I added the function of the solenoid & the wire colour:
And here is the pinout of the solenoid valve connector:
Edit 27 October 2020: changes in pictures of A342E.