Contents: General information ⇊ Torque converter, gears and clutches ⇊ Electronic control ⇊ Hydraulic drive control ⇊ Gear shift control mechanism ⇊ Locking mechanism ⇊ Gear selection ⇊ Automatic transmission range…⇊ Transfer case (4WD) ⇊
General information
The automatic transmission combines a 3-piece torque converter and a three-shaft electronically controlled unit that provides 4 forward gears and 1 reverse gear. The gearbox assembly is located in line with the engine.
Torque converter, gears and clutches
The torque converter consists of a pump, turbine and stator assembly, located in a single unit. They are connected to the engine crankshaft and rotate with it. A toothed ring gear is attached to the outer part of the torque converter, which engages with the starter pinion when the engine starts. The torque converter as a whole serves as a flywheel to transmit power to the transmission input shaft; the gearbox has three parallel shafts: a drive shaft, an intermediate shaft and a driven shaft. The drive shaft is coaxial with the engine crankshaft, and it contains the 3rd and 4th gear clutches and gears for 3rd, 4th gear, reverse and an intermediate gear. The reverse gear of the drive shaft is made integral with the 4th gear gear of the drive shaft. The intermediate shaft contains gears for 1st, 2nd, 3rd, 4th gears, reverse, parking gear and final drive gear. The main transmission gear is made integral with the intermediate shaft. The intermediate shaft 4th gear and intermediate shaft reverse gear can lock onto the intermediate shaft, allowing the transmission to move in 4th gear or reverse, depending on how you move the selector lever. On the driven shaft there are clutches for 1st and 2nd gears and gears for 1st, 2nd gears and an intermediate gear. The idler shaft is located between the drive and driven shafts and the intermediate gear transmits power from the drive shaft to the driven shaft. The gears on the drive and driven shafts are in constant engagement with the gears on the intermediate shaft. When certain combinations of gears in the gearbox are engaged by means of clutches, power is transmitted from the input and output shafts to the intermediate shaft and provides movement in the [D],[2],[1] and [R] ranges,
Electronic control
The electronic control system consists of a powertrain control unit (PCM), sensors and solenoid valves. Electronic control of gear shifting and locking provides convenience in all driving modes. The Grade Logic Control System is also provided to control shifting in the D range when driving uphill or downhill. The PCM is located under the instrument panel behind the glove box.
Hydraulic drive control
The control valve box contains the main valve body, the control valve body and the servo valve body. They are bolted to the torque converter housing. The main valve body contains the manual control valve, the A, B, C and E shift valves, the pressure reducing valve, the lock-up control valve, the cooler stop valve, the servo valve and the ATE pump gears. The control valve body contains the control valve, the torque converter stop valve, the shift lock valve and the 1st gear accumulator. The servo valve housing contains the servo valve, the SRV valve, the 2nd, 3rd and 4th gear accumulators and the gear shift solenoid valves for valves A, B, C and E. Fluid from the regulator passes through the manual control valve and is supplied to the various control valves. Fluid is supplied to the 1st and 3rd gear clutches through the corresponding tubes, and to the 2nd and 4th gear clutches - from the internal hydraulic circuit.
Gear shift control mechanism
The control of gear shifting, gear shift solenoid valves A, B, C and E and the solenoid valves for regulating the pressure in the automatic transmission clutches is carried out by the command of the PCM unit based on signals received from various sensors and switches located throughout the vehicle. The shift solenoid valves change the position of the shift valves by switching the channel that supplies hydraulic pressure to the clutch. Electrovalves A, B and C for regulating pressure in automatic transmission clutches create pressure in the clutches, engaging them with the corresponding gears. The pressure from the solenoid valves regulating the pressure in the automatic transmission clutches is also supplied to the gear shift valves to close and open the channel.
Locking mechanism
The locking mechanism is activated in position [D] (3rd and 4th gears) and in position [D] in the "overdrive off" mode (3rd gear). Pressurized fluid flows through a hole from the rear of the torque converter, forcing the torque converter clutch piston against the torque converter cover. In this case, the drive shaft rotates at the same frequency as the engine crankshaft. Together with the hydraulic drive, the RCM unit optimizes the synchronization and volume of fluid in the locking mechanism. When the PCM energizes shift solenoid valve E, the pressure from this solenoid valve energizes and deenergizes the shift lock valve. The solenoid valve A for regulating the pressure in the automatic transmission clutches and the locking control valve regulate the volume of fluid in the locking mode.
Gear selection
The selector lever has six positions: [P] PARK, [R] REVERSE, [N] NEUTRAL, [D] DRIVE in the range from 1st to 4th gear with Over-drive mode ("overdrive engaged") and in the range from 1st to 3rd gear with Over-drive OFF mode ("overdrive disengaged"), [2] 2nd gear and [1] 1st gear.
| Position | Description |
| [R] PARK | The front wheels are locked; the parking brake pawl is engaged with the parking gear on the intermediate shaft. All clutches are disengaged. |
| [R] REVERSE | Reverse: the reverse gear selector lever is engaged with the intermediate shaft reverse gear and the 4th gear clutch is engaged. |
| [N] NEUTRAL | All clutches are disengaged. |
| [D] DRIVE with Overdrive mode (from 1st to 4th gear) | Normal driving: starts in 1st gear, automatically shifts to 2nd, 3rd, then 4th gear depending on vehicle speed and throttle position. Downshifting in the range from 3rd to 2nd and 1st gears when decelerating to a complete stop. The locking mechanism operates in 3rd and 4th gears. |
| [D] DRIVE with Overdrive OFF mode(from 1st to 3rd gear) | For rapid acceleration on the motorway and normal driving, for driving uphill and downhill: starting off in 1st gear, automatically shifting to 2nd, then 3rd gear depending on vehicle speed and throttle position. Downshifting between 2nd and 1st gear when decelerating to a complete stop. The locking mechanism operates in 3rd gear. |
| [2] SECOND | It is used for engine braking and increasing traction, starting off on roads with loose surfaces or on slippery roads: it remains in 2nd gear and does not shift up or down. |
| [1] FIRST | For engine braking: remains in 1st gear and does not shift up. |
By using a sliding type engine start interlock switch, starting is only possible from positions [P] and [N].
Automatic transmission range indicator
The indicator on the instrument panel shows the selected gear range of the automatic transmission.
Transfer case (4WD)
The transfer mechanism consists of the transfer case drive gear in the differential, the transfer case shaft, and the transfer case drive gear (hypoid gear), transfer case driven gear shaft (hypoid gear) and connecting flange. The transfer case assembly is located at the rear of the gearbox, next to the differential. The transfer case drive pinion in the differential drives the transfer case drive pinion shaft and the transfer case driven pinion(hypoid gear), and the transfer case drive gear (hypoid gear) drives the driven gear shaft of the transfer case (hypoid gear). Power from the transfer case pinion in the differential is transmitted to the rear differential via the transfer case and driveshaft.