Federal safety regulators are expanding a probe of FCA vehicles, primarily the Jeep Grand Cherokee, due to problems with the transmission shifting mechanism.

Federal safety regulators are expanding a probe of more than 850,000 Fiat Chrysler cars and SUVs because the design of their electronic shifters could lead to confusion by drivers who exit the vehicles without putting them in park.

The National Highway Traffic Safety Administration says it has received 314 complaints about the problem, along with reports of 121 crashes and 30 injuries. Most of the incidents involve Jeep Grand Cherokee SUVs which account for about half of the models under investigation.

The design of the new gear shift levers is “not intuitive and provides poor tactile and visual feedback to the driver,” according to a preliminary NHTSA report, “increasing the potential for unintended gear selection.”

Until recently, shifting a vehicle was a relatively straightforward and conventional process, the only difference being where the gear level was mounted and whether the transmission was manual or automatic. But in their push to improve fuel economy, many manufacturers have adopted more advanced transmissions, some with eight, nine and even 10 speeds. And they frequently use non-traditional shifters.

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Ford and Jaguar, among others, now have begun using dial-like shift knobs. BMW and Mercedes-Benz have adopted small, steering wheel mounted stalks that use different patterns than traditional, mechanical shifters. And while the new Fiat Chrysler shift levers might look more like a traditional design they require different movements to operate. The lever is no longer simply pulled towards or pushed away from the driver, cycling through Park, Reverse, Neutral and Drive.

And that is where the confusion comes in. “The shift knob is a real problem,” the owner of a 2015 Grand Cherokee from Enumclaw, Washington, stated in a complaint filed with NHTSA. “It terrifies me to drive this vehicle.”

The safety agency initially launched its probe last August, initially focusing on 408,000 Jeep Grand Cherokees. It has now upgraded that to an engineering analysis, one step short of a full recall.

And NHTSA is now looking at 856,000 Fiat Chrysler vehicles using the transmission, including not only the Jeep Grand Cherokee but also the 2012 to 2014 Dodge Charger and the Chrysler 300. All of those models are equipped with the “E-shift” lever.

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FCA says it is cooperating with the investigation. The automaker recently took steps to improve its handling of safety-related issues after being hit with record fines for a series of lapses. Among other things, it has appointed a new safety czar authorized to take more immediate steps when safety problems are reported.

Fiat Chrysler is by no means the only maker to have problems with transmissions. There have been numerous issues over the years, including conventional levers that sometimes fail to properly lock into the Park position.

Within just the last two years, manufacturers including Ford, General Motors, Kia and Hyundai have had to collectively recall more than 1 million vehicles due to a variety of transmission problems.

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But safety experts are growing increasingly concerned about the design of new electronic shifters, such as those used by FCA, BMW, Mercedes and others, that don’t follow the familiar shift patterns that motorists have grown accustomed to. A major recall at Fiat Chrysler could signal the industry to rethink transmission shifter design.