Components
GENERALThe automatic transmission is a combination of a 3-element torque converter and triple-shaft electronically controlled automatic transmission which provides 4 speeds forward and 1 speed reverse. The entire unit is positioned in line with the engine.
TORQUE CONVERTER, GEARS AND CLUTCHES
The torque converter consists of a pump, turbine and stator assembled in a single unit. They are connected to the engine crankshaft so they turn together as a unit as the engine turns. 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 while transmitting 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 engine crankshaft. The mainshaft includes the 3rd, and 4th clutches, and gears for 3rd, 4th, reverse and idler (Reverse gear is integral with 4th gear). The countershaft includes the gears for, 1st, 2nd, 3rd, 4th, reverse, parking and idler. The secondary shaft includes the 1st, 1st-hold and 2nd clutches, and gears for 2nd, 1st and idler. The 4th and reverse gears can be locked to the countershaft at its center, 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 (TCM), sensors, a linear solenoid and four solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The TCM is located below the dashboard, under the front lower panel on the passenger's side.
HYDRAULIC CONTROL
The hydraulic control system is controlled by the ATF pump, valves and accumulators in the valve bodies. Fluid from the ATF pump passes through the regulator valve and the manual valve to the various control valves. The clutches receive fluid from their respective ATF feed pipes or internal hydraulic circuit. The main valve body, the secondary valve body, the regulator valve body, the servo body and the lock-up valve body are bolted onto the torque converter housing as an assembly. The accumulator body is bolted onto the torque converter housing next to the other valve bodies. The throttle valve body is joined with the linear solenoid. The throttle valve body/linear solenoid assembly is bolted onto the transmission housing. The shift control solenoid valves and lock-up control solenoid valves are bolted onto the outside of the torque converter housing. The hydraulic circuit of the throttle valve body, shift control solenoid valves and lock-up control solenoid valves is connected with the internal hydraulic circuit.
SHIM CONTROL MECHANISM
Input from various sensors located throughout the vehicle determines which shift control solenoid valve the TCM will activate. Activating a shift control solenoid valve changes modulator pressure, causing a shift valve to move. This pressurizes 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 D position in 3rd, pressurized fluid is drained from the back of the torque converter through a fluid 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 TCM 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 the throttle valve. When lock-up control solenoid valves A and B activate, the modulator pressure changes. Lock-up control solenoid valves A and B are mounted on the torque converter housing, and are controlled by the TCM.
GEAR SELECTION
The shift lever has seven positions: PARK, REVERSE, NEUTRAL, D4 1st through 4th gear ranges, D3 1st through 3rd gear ranges, [2] 2nd gear and [1] 1st gear. Starting is possible only in P and N positions through the use of a slide-type, neutral-safety switch.
AUTOMATIC TRANSAXLE (A/T) GEAR POSITION INDICATOR
The A/T gear position indicator in the instrument panel shows which gear has been selected without having to look down at the console.