But the Sidecar band isn’t staying together.

Jahan Khanna, who co-founded Sidecar in 2011 with Sunil Paul, has left GM after to join Uber, Fortune has learned. His departure comes after growing disagreements between him and GM (GM), according to people close to the matter. GM declined to comment.

Khanna is joining Uber as the product lead of the Vehicle Solutions growth team and starts his new role on Monday, Uber confirmed to Fortune. Uber’s Vehicle Solutions includes initiatives like its car-leasing program for drivers.

Uber, which continues to battle rival and GM partner Lyft, no doubt finds value in Khanna’s experience and expertise from founding a company with similar aims. Khanna may also have insight into GM’s car-sharing plans, which may also be of value.

“We are committed to making it easier for more people to drive with Uber. As part of that, we are continuing to invest in Uber’s Vehicle Solutions Program. We are excited to welcome Jahan to the team leading that charge,” an Uber spokeswoman told Fortune.

Get Data Sheet, Fortune’s technology newsletter.

Despite getting an early start in the ride-hailing game and raising $39 million, Sidecar increasingly struggled to compete with Uber and Lyft, which have raised billions of dollars in funding over the years. Last year, Sidecar tried to salvage its business by shifting to providing deliveries for merchants. It shut down in December, partly blaming its struggles on Uber’s massive size, resources, and ruthlessness. It then sold itself to GM.

That deal came just as GM was forging a partnership with Lyft. In January, GM announced that it would invest $500 million in Lyft as well as collaborate with the startup to eventually deploy autonomous cars into Lyft’s service offerings. GM is also developing its own car-sharing service, a project on which Khanna worked.

Lyft and Uber’s have been waging a ride-hailing war for years, including aggressive attempts to steal each other’s drivers along with allegations that Uber repeatedly ordered and canceled Lyft rides to cause trouble. Six months ago, that war took an international turn when Lyft teamed up with ride-hailing services Didi Kuaidi in China, Ola in India, and Grab in southeast Asia to let their respective customers use each other’s services.

As the auto industry plans for a future of self-driving cars, so does Uber and Lyft. Uber has invested millions into its own research and development of the technology, partly through a partnership with Carnegie Mellon University.

Lyft, on the other hand, is leaning on GM and its autonomous driving ambitions.