Sedan
DESCRIPTIONThe Automatic Transmission is a combination of a 3-element torque converter and dual-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 two parallel shafts, the mainshaft and countershaft. The mainshaft is in line with the engine crankshaft.
The mainshaft includes the clutches for 1st, and 2nd/4th, and gears for 3rd, 2nd, 4th, Reverse and 1st (3rd gear is integral with the mainshaft, while reverse gear is integral with 4th gear).
The countershaft includes 3rd clutch and gears for 3rd, and 4th, Reverse and 1st.
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. When certain combinations of gears in the transmission are engaged by the clutches, power is transmitted from the mainshaft to the countershaft to provide (S3),(S4),(D),(2) and (R).
Electronic Control
The electronic control system consists of an automatic control unit, sensors, and 4 solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.
The A/T control unit is located under the passenger's seat.
HYDRAULIC CONTROL
The valve assembly includes the main valve body, secondary valve body, servo valve body, regulator valve body and lock-up shift valve body.
They are bolted to the torque converter case as an assembly.
The main valve body contains the manual valve, 1-2 shift valve, 2-3 shift valve, 3-4 shift valve, pressure relief valve, orifice control valve torque converter check valve, and oil pump gear.
The secondary valve body includes the CPC valve 4-3 kickdown valve, 4-2 kickdown valve, modulator valve and the 2nd orifice control valve.
The servo valve body contains the accumulator pistons and throttle valves A and B. The regulator valve body contains the lock-up timing valve B pressure regulator valve and lock-up control valve. Fluid from the regulator passes through the manual valve to the various control valves.
The lock-up shift valve body contains a cooler relief valve and lock-up shift valve. The 1st, 3rd and 4th clutches receive oil from their respective feed pipes.
SHIFT CONTROL MECHANISM
Input from various sensors located throughout the car determines which shift control solenoid valve the A/T control unit 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 (S4) or (D), in 2nd, 3rd and 4th, pressurized 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, an electronic control unit optimizes the timing of the lock-up mechanism.
The lock-up shift valve body controls 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 A/T control unit.
GEAR SELECTION
The selector lever has six positions: (P) PARK, (R) REVERSE, (N) NEUTRAL, (D) or (S4) 1st through 4th gear ranges, (S3) 1st through 3rd gear ranges, and (2) 2nd gear.
Position Description
(P) PARK:
Front wheels locked; parking pawl engaged with parking gear on countershaft. All clutches released.
(R) REVERSE:
Reverse; reverse selector engaged with countershaft reverse gear and 4th gear clutch locked.
(N) NEUTRAL:
All clutches released.
(D) DRIVE and (S4) SPORTS (1 through 4):
General driving; starts oft in 1st, shifts automatically to 2nd, 3rd, then 4th,depending on vehicle speed and throttle position. Downshifts through 3rd, 2nd and 1st on deceleration to stop.
The lock-up mechanism comes into operation in 2nd, 3rd and 4th when the transmission is in (D) and (S4).
(S3) SPORTS (1 through 3):
For rapid acceleration at highway speeds and general driving; starts off in 1st, shifts automatically to 2nd, then 3rd (S3), and then 4th (S4) depending on vehicle speed and throttle position. Downshifts through lower gears on deceleration to stop.
(2) SECOND:
For engine braking or better traction starting off on loose or slippery surfaces; stays in 2nd gear, does not shift up or down.
Starting is possible only in (P) and (N) through use of a slide-type, neutral-safety switch.
POSITION INDICATOR
A position indicator in the instrument panel shows what gear has been selected without having to look down at the console.