125 / 125C Automatic Transmission Principles of Operation and Systematic Troubleshooting

This book can help anyone to understand the basic operation of a transmission and how to troubleshoot it properly. The only difference between the 125 and 125 c is the torque converter clutch hydraulic and electrical circuits. With this book you can understand what is failing with the transmission before tear down.

Section 1 starts with a general description of the transmission and its components. It then progresses into an understanding of the torque converter, power flow, then summarizes the power flow.

Next is the hydraulic system and complete hydraulic circuits. Then finally into the torque converter clutch electrical controls for both applied and released states.

Section 2 contains systematic troubleshooting flow charts for every possibility of malfunction. It includes the proper way to use a pressure gauge with expected readings, plus road test procedures.

It then progresses into explaining the causes of problems that resulted in a failure, with flow charts. Exploded views of the transmission and valve body are included.