Stellantis Outlines New Method for Transmission Fluid Drainage With Patented System

Stellantis has been granted a patent for a new method of draining and replacing transmission fluid in automatic transmissions, reports Mopar Insiders.

Officially issued by the United States Patent and Trademark Office on Jan. 28, 2025, the patent is for a system containing an electrically powered auxiliary oil pump that does not require the engine to be turned on during service.

Using an automatic transmission equipped with a torque converter, gearbox, and an electro-hydraulic control system, power is transferred from the engine to the drive axles. A transmission control module oversees gear shifts through engaging or disengaging clutches as needed. 

The patented system also contains a mechanically driven oil pump and an auxiliary oil pump powered by an electric motor—the latter of which allowing for fluid circulation when the engine is off.

To perform service on the patented system, technicians will need to use a service computer to initiate an oil drain or flush service. Then, the drain plug is to be removed, and the drain hole opened, followed by the auxiliary oil pump being activated, and the old transmission fluid being circulated and ejected through the drain hole.

Adequate fluid drainage is determined based on several factors, including a hydraulic solenoid that detects fluid flow changes; comparing the pump’s runtime against a pre-set time threshold; the amount of drained fluid; changes in pump load; and a technician verifying minimal fluid has exited the drain hole. When drainage is completed, the auxiliary pump deactivates.

Stellantis has said this system builds upon traditional, gravity-based drainage methods, and allows for a more thorough flush, with debris being actively flushed out. Additionally, the company argued the system improves safety by not requiring the engine to run, takes less time, and allows for less reliance on external equipment. It’s possible it could be adapted for more hydraulic systems than just automatic transmissions as well.