Description & Operation: Introduction

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4R70W is a 4-speed, automatic transmission with electronic shift, converter clutch and line pressure controls. It uses a double-pinion compound gearset to produce 4 forward speeds and reverse. 4R70W also uses 2 bands, 2 one-way roller clutches and 4 friction clutches to hold or drive the planetary gearset members.

Shift control solenoids provide gear selection and are controlled by the Powertrain Control Module (PCM). Input signals from sensors are sent to the PCM. The PCM can determine when the time and conditions are right for a shift or converter clutch application. The PCM can also determine line pressure needed to optimize shift feel.

The PCM has self-diagnostic capabilities. Diagnostic Trouble Codes (DTC) for faulty engine and transmission sensors, switches and circuits are stored in the PCM, and may be retrieved to aid diagnosis and repair.