A newly published patent filing from Stellantis suggests the automaker is working on a way to bring planetary gear hybrid technology—the kind currently humming along in the Chrysler Pacifica Hybrid—into the rough-and-tumble world of serious four-wheel-drive vehicles. Think Jeeps built to crawl over rocks without sacrificing the efficiency gains of a power-split hybrid system.
The patent was submitted to the United States Patent and Trademark Office back in July 2023 and published on February 6. It lays out a technical approach that could bridge a gap Stellantis has been wrestling with for years.
Here’s the problem. The Pacifica Hybrid uses a planetary power-split system to blend its 3.6-liter V-6 with two electric motors, both of which can double as generators. It works beautifully in a minivan that never leaves pavement. But pair that same architecture with a traditional mechanical transfer case—the kind needed for legitimate off-road capability—and things get ugly fast.
Stellantis acknowledges as much in the filing. Rough shifts between high and low range. Difficulty engaging low-range gear splines when the vehicle is stopped. Synchronization headaches while crawling in low range. These aren’t minor annoyances; they’re dealbreakers for any vehicle wearing a Jeep badge and Trail Rated sticker.
That’s almost certainly why the current Jeep Wrangler 4xe and Grand Cherokee 4xe plug-in hybrids went a completely different route. Those models keep their conventional mechanical four-wheel-drive systems and eight-speed automatic transmissions largely intact, wedging one electric motor into the transmission housing and bolting a smaller motor-generator onto the engine’s crankshaft. It works, and it sells, but it’s not the most elegant or efficient solution.
The patent describes what amounts to splitting the difference. Stellantis wants to mate a planetary-gear power-split configuration with a two-speed transfer case from a traditional four-wheel-drive system, using a disconnect device that can decouple the engine and electric motors from the driveline entirely. The clever part is using motor torque to synchronize the input and output shaft speeds of the transfer case, letting the electric motors smooth out the very transitions that make current combinations so clunky.
If it works as described, the implications for future Jeep products could be significant. A planetary hybrid drivetrain that plays nicely with a proper transfer case could deliver meaningfully better fuel economy than the current 4xe setup while maintaining the low-range crawling capability that Jeep enthusiasts demand. It’s the kind of engineering that could make a hybrid Wrangler feel less like a compromise and more like an evolution.
The timing is interesting, too. Jeep’s 4xe plug-in hybrids have generally sold well despite the broader market’s lukewarm reception of plug-in technology. Reports have also surfaced that Jeep is considering conventional hybrids—no charge port, no plugging in—to sell alongside the 4xe models in the United States. A refined planetary system could underpin either approach.
Of course, a patent filing is not a production announcement. Automakers patent speculative technology all the time, and plenty of clever ideas never make it past the engineering lab. But this one addresses a real, documented shortcoming with existing hardware, and it comes from a company that desperately needs to modernize its powertrain lineup while protecting the off-road credibility that keeps Jeep buyers loyal.
Stellantis hasn’t commented publicly on the filing. But somewhere in Auburn Hills, engineers are clearly trying to solve a puzzle that could define the next generation of electrified Jeeps—vehicles that can sip fuel on the highway and still conquer a mountain trail without breaking a sweat.
