Honda Odyssey 2004. Manual — part 156
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General Operation
Torque Converter, Gears, and Clutches
Electronic Control
Hydraulic Control
Shift Control Mechanism
Lock-up Mechanism
14-18
Automatic Transmission
System Description
The automatic transmission is a combination of a 3-element torque converter and triple-shaft electronically controlled
unit which provides 4 speeds forward and 1 reverse. The entire unit is positioned in line with the engine.
The torque converter consists of a pump, turbine, and stator assembly in a single unit. The converter housing (pump)
is connected to the engine crankshaft and turn 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, 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 the
4th gear). The countershaft includes the final drive, 1st, 3rd, 4th, reverse, 2nd, park, and idler gears (the final drive gear
is integral with the countershaft). The secondary shaft includes the 1st and 2nd clutches, and gears for 1st, 2nd, and
idler. The countershaft 4th gear and the countershaft reverse gear can be locked to the countershaft at its center,
providing 4th gear or reverse, depending which way the selector moved. The gears on the mainshaft and the
secondary shaft 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 through the mainshaft, then to the secondary shaft to
the countershaft to provide drive.
The electronic control system consists of the powertrain control module (PCM), sensors, and six solenoid valves.
Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The PCM is located
below the dashboard, under the front lower panel behind the center console.
The valve bodies include the main valve body, the regulator valve body, the servo body, and the accumulator body.
They are bolted to the torque converter housing. The main valve body contains the manual valve, the modulator valve,
the shift valve C, the shift valve D, the shift valve E, the servo control valve, the torque converter check valve, the
reverse Clutch Pressure Control C (CPC) valve, the lock-up shift valve, the relief valve, the cooler check valve, and the
ATF pump gears. The regulator valve body contains the regulator valve, the lock-up timing valve, and the lock-up
control valve. The servo body contains the servo valve, the shift valve A, the shift valve B, the CPC valves A and B, and
3rd and 4th accumulators. The accumulator body contains the 1st and 2nd accumulators and lubrication check valve.
Fluid from the regulator passes through the manual valve to the various control valves. The 1st, 3rd, and 4th clutches
receive fluid from their respective feed pipes, and the 2nd clutch receives fluid from the internal hydraulic circuit.
To shift gears, the PCM controls shift solenoid valves A, B, and C, and A/T clutch pressure control solenoid valves A
and B while receiving input signals from various sensors and switches located throughout the vehicle. The shift
solenoid valves shift the positions of the shift valves to switch the port leading hydraulic pressure to the clutch. The
A/T clutch pressure control solenoid valves A and B control the CPC valves A and B to shift smoothly between lower
gear and higher gear. This pressurizes a line to one of the clutches, engaging the clutch and its corresponding gear.
The lock-up mechanism operates in the D4 position (3rd and 4th) and D3 position (3rd). The pressurized fluid is
drained from the back of the torque converter through a fluid passage, causing the torque converter clutch 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. When the torque
converter clutch solenoid valve activates, modulator pressure changes to switch lock-up on and off. The lock-up
control valve and the lock-up timing valve control the amount of lock-up according to A/T clutch pressure control
solenoid valves A and B. The torque converter clutch solenoid valve is mounted on the torque converter housing, and
A/T clutch pressure control solenoid valves A and B are mounted on the transmission housing. They are all controlled
by the PCM.
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Gear Selection
Position
Description
Automatic Transaxle (A/T) Gear Position Indicator
14-19
The shift lever has seven positions; P: PARK, R: REVERSE, N: NEUTRAL, D4: 1st through 4th gear ranges, D3: 1st
through 3rd gear ranges, 2: 2nd gear, and 1: 1st gear.
P: PARK
Front wheels locked; park pawl engaged with park gear on countershaft. All clutches are
released.
R: REVERSE
Reverse; reverse selector engaged with countershaft reverse gear and 4th clutch locked.
N: NEUTRAL
All clutches are released.
D4: DRIVE
(1st through 4th)
General driving; starts off in 1st, shifts automatically to 2nd, 3rd, then 4th, depending on
vehicle speed and throttle position. Downshift through 3rd, 2nd, and 1st on deceleration to
stop. The lock-up mechanism operates in 3rd and 4th gear.
D3: DRIVE
(1st through 3rd)
Used for rapid acceleration at highway speeds and general driving; up-hill and down-hill
driving; starts off in 1st, shifts automatically to 2nd, then 3rd, depending on vehicle speed and
throttle position.
Downshifts through 2nd to 1st on deceleration to stop. The lock-up mechanism operates in 3rd
gear only.
2: SECOND
Used for engine braking or better traction starting off on loose or slippery surfaces; stays in
2nd gear, does not shift up or down.
1: FIRST
Used for engine braking; stays in 1st gear, does not shift up.
Starting is possible only in the P and N positions because of the slide-type neutral-safety switch.
The A/T gear position indicator in the instrument panel shows which shift lever position has been selected.
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Clutches
1st Clutch
2nd Clutch
3rd Clutch
4th Clutch
14-20
Automatic Transmission
System Description (cont’d)
The 4-speed automatic transmission uses hydraulically-actuated clutches to engage or disengage the transmission
gears. When hydraulic pressure is introduced into the clutch drum, the clutch piston moves. This presses the friction
discs and steel plates together, locking them so they don’t slip. Power is then transmitted through the engaged clutch
pack to its hub-mounted gear. Likewise, when the hydraulic pressure is bled from the clutch pack, the piston releases
the friction discs and the steel plates, and they are free to slide past each other. This allows the gear to spin
independently on its shaft, transmitting no power.
The 1st clutch engages/disengages 1st gear, and is located at the middle of the secondary shaft. The 1st clutch is
joined back-to-back to the 2nd clutch. The 1st clutch is supplied hydraulic pressure by its ATF feed pipe within the
secondary shaft.
The 2nd clutch engages/disengages 2nd gear, and is located at the middle of the secondary shaft. The 2nd clutch is
joined back-to-back to the 1st clutch. The 2nd clutch is supplied hydraulic pressure through the secondary shaft by a
circuit connected to the internal hydraulic circuit.
The 3rd clutch engages/disengages 3rd gear, and is located at the middle of the mainshaft. The 3rd clutch is joined
back-to-back to the 4th clutch. The 3rd clutch is supplied hydraulic pressure by its ATF feed pipe within the mainshaft.
The 4th clutch engages/disengages 4th gear, as well as reverse gear, and is located at the middle of the mainshaft. The
4th clutch is joined back-to-back to the 3rd clutch. The 4th clutch is supplied hydraulic pressure by its ATF feed pipe
within the mainshaft.
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17
Transmission Cutaway View
14-21
MAINSHAFT
MAINSHAFT
IDLER GEAR
MAINSHAFT
REVERSE GEAR
MAINSHAFT
4TH GEAR
4TH CLUTCH
3RD CLUTCH
MAINSHAFT
3RD GEAR
ATF PUMP DRIVEN GEAR
RING GEAR
TORQUE CONVERTER
LOCK-UP CLUTCH
PISTON
DRIVE PLATE
FINAL DRIVE GEAR
COUNTERSHAFT
3RD GEAR
COUNTERSHAFT
1ST GEAR
DIFFERENTIAL
ASSEMBLY
FINAL DRIVEN GEAR
SECONDARY SHAFT
1ST GEAR
1ST CLUTCH
2ND CLUTCH
SECONDARY SHAFT
2ND GEAR
SECONDARY SHAFT
IDLER GEAR
SECONDARY
SHAFT
COUNTERSHAFT
4TH GEAR
REVERSE
SELECTOR
PARK GEAR
REVERSE
SELECTOR HUB
COUNTERSHAFT
COUNTERSHAFT
IDLER GEAR
COUNTERSHAFT
2ND GEAR
COUNTERSHAFT
REVERSE GEAR
PITOT PIPE
LUBRICATION
PITOT PIPE
PITOT FLANGE
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