Four-wheel drive vehicles often feature low-range transfer cases, but this trail-centric gearing often can’t be engaged on the move. Stellantis is working on a way to do this—in hybrid vehiclesat least.
In a patent application published by the United States Patent and Trademark Office (USPTO) on June 4, 2024, and originally filed by Stellantis on July 31, 2023, the automaker discusses idle speed changes in motion using a hybrid system in which two electric motors connect to an internal combustion engine via a planetary gearset, while retaining a traditional transfer case and rear differential.
![Patent image of Stellantis in-motion 4WD Lo shift Patent image of Stellantis in-motion 4WD Lo shift](https://thegurumedia.com/wp-content/uploads/2024/07/stellantis-in-motion-4wd-lo-shift-patent-image_100934695_l.jpg)
Patent image of Stellantis in-motion 4WD Lo shift
In such a system, the two motors are used to synchronize the speed of the engine and a transmission output shaft to perform smooth shifts into and out of low range while the vehicle is in motion. One motor would be connected to the center sun gear of the planetary gearset and would apply torque to the gear shaft to moderate engine speeds. The second motor would do the same for the transmission output shaft.
Sensors would monitor the speeds of the engine, transmission output shaft, driveshaft, and wheels, sending instructions to a controller as needed to ensure everything is in sync. To engage low gear while movingsignals would be sent to rotate the low gear at the same speed as the wheels, eliminating the speed differential that normally makes it difficult to shift into low gear while driving.
![Patent image of Stellantis in-motion 4WD Lo shift Patent image of Stellantis in-motion 4WD Lo shift](https://thegurumedia.com/wp-content/uploads/2024/07/stellantis-in-motion-4wd-lo-shift-patent-image_100934694_l.jpg)
Patent image of Stellantis in-motion 4WD Lo shift
If implemented, this would be a great development for the old school four-wheel drive systems. The additional gear reduction created by low range further increases low-speed traction, making it crucial for off-roading, but it’s not useful at higher speeds. And now, most production vehicles require drivers to stop and shift into neutral to engage or disengage low range.
It makes sense that Jeep’s parent company would propose this feature, though whether it will actually be produced is another question. Current Jeep 4xe plug-in hybrids use a different arrangement of electric motors, with a main drive motor on the input shaft of an 8-speed automatic transmission, but no motor on the output shaft (a second belt-connected motor helps power accessories, however). It could be implemented with the plug-in hybrid powertrain series inclined to the next Jeep Wranglerhowever.