Torque Converter, Gears and Clutches

The Automatic Transmission is a combination of a 3 – element torque converter and triple – shaft electronically controlled transmission which provides 4 forward speeds and reverse. The unit is positioned in line with the engine.

Torque Converter, Gears and Clutches

The torque converter assembly comprises an impeller, turbine and stator contained within a housing connected to the crankshaft via a drive plate. Around the outside of the torque converter is a ring gear which meshes with the starter pinion when the engine is being started. The entire torque converter assembly serves as a flywheel and transmits power to the transmission mainshaft. The transmission has three parallel shafts: the mainshaft, the countershaft, and the secondary shaft. The mainshaft is in line with the crankshaft.

The mainshaft carries the clutches for 3rd and 4th, and gears for 3rd, 4th, Reverse and Idler (Reverse gear is integral with 4th gear).

The countershaft carries the 1st – hold clutch and gears for 2nd, 3rd, 4th, Reverse, 1st, Idler and Parking.

The secondary shaft carries the 1st and 2nd clutches, and gears for 2nd, 1st and Idler.

The 4th and reverse gears can be locked to the countershaft at its centre, providing 4th gear or Reverse, depending on which way the selector is moved.

The gears on the mainshaft are in constant mesh with those on the countershaft and the secondary shaft. When certain combinations of gears in the transmission are engaged by the clutches, power is transmitted from the mainshaft to the countershaft to provide D4, D3, 2, 1 and R positions.

Electronic Control

The electronic control system consists of the transmission control module, sensors, and 4 solenoid valves. Shifting and lock – up are electronically controlled for comfortable driving under all conditions. The transmission control module is located in the passenger’s footwell.

Hydraulic Control

The valve body assemblies comprise the main valve body, secondary valve body, servo valve body, regulator valve body, throttle valve body and 1st/2nd accumulator body. They are bolted to the torque converter housing as an assembly. The main valve body contains the manual valve, 1 – 2 shift valve, 2 – 3 shift valve, cooler relief valve, lock – up shift valve, lock – up control valve, 3 – 2 kick – down valve, modulator valve, clutch pressure control valve and oil pump gears.

The secondary valve body includes the 4th exhaust valve, 3rd kick – down valve, 3 – 4 shift valve, servo control valve, orifice control valve and the 2nd orifice control valve.

The servo valve body contains the accumulator pistons and servo valve. The regulator valve body contains the regulator valve, torque converter check valve, and lock – up timing valve. The throttle valve body contains the throttle valve B and relief valve. Fluid from the regulator passes through the manual valve to the various control valves.

The clutches receive oil from their respective feed pipes or internal hydraulic circuit.

Shift Control Mechanism

Input from various sensors located throughout the car determines which shift control solenoid valve the transmission control module will activate. Activating a shift control solenoid valve changes modulator pressure, causing a shift valve to move. This pressurises a line to one of the clutches, engaging that clutch and its corresponding gear.

Lock – up Mechanism

In D4 position, in 2nd, 3rd and 4th, and D3 position in 3rd, pressurised fluid is drained from the back of the torque converter through an oil passage causing the lock – up piston to be held against the torque converter cover. As this takes place, the mainshaft rotates at the same speed as the engine crankshaft. Together with hydraulic control, the transmission control module optimizes the timing of the lock – up mechanism. The lock – up valves control the range of lock – up according to lock – up control solenoid valves A and B, and throttle valve B. When lock – up control solenoid valves A and B activate, modulator pressure changes. Lock – up control solenoid valves A and B are mounted on the torque converter housing, and are controlled by the transmission control module.