725.0, 9G-TRONIC, NAG3

The Mercedes-Benz 725.0, commonly known as 9G-TRONIC or NAG3, is a 9-speed electronically controlled automatic transmission developed for longitudinal-engine applications. Introduced in the Mercedes-Benz E 350 BlueTEC, it was designed as the successor to the 7G-TRONIC family and uses a torque converter with lock-up clutch, four planetary gearsets and six shift elements to provide nine forward ratios. Mercedes-Benz's own technical documentation confirms the 725.0 architecture and its approximately 9.15:1 overall ratio spread.

Specification: 9-speed automatic • Mercedes-Benz 725.0 • 9G-TRONIC / NAG3 • Longitudinal installation • Rear-wheel-drive and 4MATIC applications • Torque converter with lock-up clutch • Four planetary gearsets • Six shift elements • Electro-hydraulic shift control • Fully integrated transmission control (VGS) • Primary mechanical oil pump plus auxiliary electric oil pump on applicable versions • Multiple torque-capacity variants including W9A400, W9A500, W9A700 and higher-capacity derivatives • Multiple calibrations depending on vehicle and engine application.

Commonly fitted across selected Mercedes-Benz C-Class, E-Class, CLS, S-Class, GLC, GLE, GLS, G-Class, SLC and V-Class applications. Different 725.0 versions were engineered for substantially different engine outputs and drivetrain configurations, with variants capable of handling up to approximately 1,000 Nm. Consequently, the vehicle VIN, complete 725.xxx transmission number and individual component identification should always be confirmed before ordering replacement parts.

Common Faults

Common 725.0 problems include electro-hydraulic valve-body/VGS faults, speed-sensor problems, pressure-control and solenoid faults, torque-converter lock-up problems and internal clutch or brake-element faults. Depending on the failure, symptoms can include harsh or delayed engagement, shift flare, incorrect or missing gears, transmission failsafe operation, juddering, slipping and abnormal torque-converter lock-up operation. Because the VGS electronics, sensors and hydraulic control system are highly integrated, correct diagnosis is particularly important before replacing individual transmission components.

Common Fault Codes