Honda 2004 Odyssey Service Manual page 675

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Automatic Transmission

System Description (cont'd)

Lock-up System

The lock-up mechanism operates in 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 controlled by

General Operation

1. Operation (clutch on)

With the torque converter clutch on, fluid in the chamber between the torque converter clutch cover and the

torque converter clutch piston is drained off, and the converter fluid exerts pressure through the piston against

the torque converter cover. As a result, the converter turbine is locked to the converter cover. The effect is to

bypass the converter, placing the vehicle in direct drive.

The power flows by way of:

Torque converter cover

Lock-up piston

Damper spring

2. Operation (clutch off)

With the torque converter clutch off, fluid flows in the reverse of CLUTCH ON. As a result, the torque converter

clutch piston moves away from the converter cover, and torque converter lock-up is released.

Torque converter cover

LOCK-UP PISTON

TORQUE CONVERTER

TORQUE CONVERTER

DAMPER SPRING

To ATF cooler

To ATF cooler

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