System Components
DESCRIPTIONThe automatic transmission is a combination of a 3-element torque converter and a dual-shaft electronically controlled automatic transmission which provides 4 speeds forward and 1 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 drive plate 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 two parallel shafts: the mainshaft and the countershaft. The mainshaft is in line with the engine crankshaft. The mainshaft includes the 1st, 2nd and 4th clutches, and gears for 4th, 2nd, 1st and reverse (3rd gear is integral with the mainshaft, while the reverse gear is integral with 4th gear). The countershaft includes the 3rd, and 1st-hold clutches, and gears for 3rd, 4th, 1st, 2nd, reverse, and parking. The secondary drive gear is integrated with the countershaft. The gears on the mainshaft are in constant mesh with those on the countershaft. When certain combinations of gears in the transmission are engaged by clutches, power is transmitted from the mainshaft to the countershaft to provide 1, 2, D3, D4, 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, behind the glove box on the passenger's side.
HYDRAULIC CONTROL
The lower valve body assembly includes the main valve body, the servo body and the shift control solenoid valves. They are bolted on the lower part of the transmission housing. Other valve bodies, the regulator valve body, the ATF pump body, the 2nd accumulator body, and the throttle valve body, are bolted to the torque converter housing. The main valve body contains the manual valve, the 1 - 2 shift valve, the 2 - 3 shift valve, the 3 - 4 shift valve, the 4th kickdown valve, the 2 - 3 orifice control valve, the 3 - 4 orifice control valve, the 4th exhaust valve, the servo control valve, and the main orifice control valve. The servo body contains the servo valve, 3rd and 4th accumulator pistons. The regulator valve body contains the regulator valve, the lock-up shift valve, and the cooler relief valve. Fluid from the regulator passes through the manual valve to the various control valves. The throttle valve body includes the throttle valve which is bolted onto the 2nd accumulator body. The 2nd accumulator piston is assembled in the 2nd accumulator body. The linear solenoid is joined with the throttle valve body. The ATF pump body contains the modulator valve, the lock-up control valve, the lock-up timing valve, and the relief valve. The torque converter check valve is located in the torque converter housing under the ATF pump body. The 1st and 1st-hold accumulator pistons are assembled in the rear cover. 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 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 hi position, in 2nd, 3rd and 4th, and in 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 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 throttle valve. When lock-up control solenoid valves A and B activate, the modulator pressure changes. The 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: P PARK, R REVERSE, N NEUTRAL; D4 1st through 4th gear ranges, D4 1st through 3rd gear ranges, 2 2nd gear and 1 1st gear.
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.