Description & Operation: Introduction

The M5DA is an electronically controlled 4-speed automatic transaxle. Transaxle contains hydraulically operated clutches, which are controlled by the Powertrain Control Module (PCM). PCM receives information from various inputs and uses this information to control solenoid assembly for proper transaxle operation.

Automatic transaxle has 4 forward speeds and one reverse. Transaxle consists of clutches, mainshaft, countershaft, shift control solenoid valves, lock-up control solenoid valves, linear solenoid and lock-up torque converter. Transaxle has a differential assembly bolted to the transaxle. Power is delivered from transaxle to the differential assembly by the extension shaft.

Lower valve body assembly consists of main valve body, secondary valve body, throttle valve body, linear solenoid, shift control solenoid valves and oil passage body. Lower valve body is bolted to transaxle housing. Other valve bodies used are regulator valve body, oil pump body and accumulator body. These valve bodies are bolted to torque converter housing.

Transaxle shifting and torque converter lock-up are controlled by PCM. PCM is located under carpet on passenger's side foot well. Transaxle shifting is related to engine torque through the linear solenoid used to operate the throttle valve. PCM controls the linear solenoid located on the throttle valve body. PCM determines appropriate shift point and activates proper shift control solenoid valve for transaxle shifting.

When gearshift lever is moved, manual valve on main valve body is moved by the shift cable. Gearshift lever also changes position of A/T gear position switch mounted on gearshift lever. The A/T gear position indicator on instrument panel contains lights to indicate which position A/T gear position switch on gearshift lever is in. The A/T gear position switch delivers an input signal to PCM to indicate gearshift lever position. PCM uses this input signal to control shift control solenoid valves. PCM determines appropriate shift point and activates proper shift control solenoid valve for transaxle shifting.

When in 2nd, 3rd, 4th and "D4" gears, torque converter lock-up exists and transaxle mainshaft rotates at same speed as engine crankshaft. Under certain conditions, torque converter lock-up clutch is applied during deceleration in 3rd and 4th gears. Torque converter lock-up is controlled by PCM. PCM receives various input signals and operates lock-up control solenoid valves. Operation of lock-up control solenoid valves controls the modulator pressure.

PCM contains an electronic control system, which stores a Diagnostic Trouble Code (DTC) if failure or problem exists in transaxle electronic control system. DTC can be retrieved to determine transaxle problem area.

Transaxle is equipped with shift and key interlock systems. Shift interlock system prevents gearshift lever from being moved from "P" position unless brake pedal is depressed and accelerator pedal is in idle position. In case of a malfunction, gearshift lever can be released by placing ignition key in release slot near gearshift lever. Key interlock system prevents ignition key from being removed from ignition switch unless gearshift lever is in "P" position. For additional information on shift and key interlock systems, see appropriate SHIFT INTERLOCK SYSTEMS article.