Component
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 1st-hold clutch and gears for 2nd, 3rd, 4th, reverse, 1st, parking and idler. The secondary shaft includes 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 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 Powertrain Control Module (PCM), sensors, and four solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The PCM located below the dashboard, under the front lower panel on the passenger side.
HYDRAULIC CONTROL
The valve bodies include the main valve body, the secondary valve body, the servo body, the regulator valve body, the throttle valve body and the 1sV2nd accumulator body. They are bolted to the torque converter housing as an assembly. The main valve body contains the manual valve, the 1-2 shift valve, the 2-3 shift valve, the cooler relief valve, the lock-up shift valve, the lock-up control valve, the main orifice control valve, the modulator valve, the CPC valve and the ATF pump gears. The secondary valve body includes the 4th exhaust valve, the 3rd kick-down valve, the 3-4 shift valve, the servo control valve, the orifice control valve and the 2nd orifice control valve. The servo body contains the accumulator pistons and the servo valve. The regulator valve body contains the regulator valve, the torque converter check valve, and the lock-up timing valve. The throttle valve body contains the throttle valve B and the relief valve. Fluid from the regulator passes through the manual valve to the various control valves. The clutches receive fluid from their respective feed pipes or internal hydraulic circuit.
SHIFT CONTROL MECHANISM
Input from various sensors located throughout the vehicle determines which shift control solenoid valve the PCM 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 D3 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 PCM 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 B. 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 PCM.
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.