Electric vehicles (EVs) do feature a differential, but it works a little differently than the differential on a gas-powered vehicle.
What a Differential Does
The term differential refers to a component of a motorized vehicle’s drivetrain. It delivers and distributes power from the engine to the wheels.
Modern transmission design uses three types of differential. Your vehicle might have a:
- Locking (front or rear) differential,
- Open differential,
- Limited slip differential.
The location of the differential varies according to transmission design. It could go in:
- Front – located between the center wheels,
- Center – located between the front and rear wheels,
- Rear – located between the rear wheels.
A vehicle corners smoothly because of its differential. Without it, you could pretty much only drive in a straight line.
What Happens When a Vehicle Turns?
When you drive in a straight line, every wheel of your car does the same amount of work, the same way. This changes when the vehicle makes a turn. When turning, the vehicle’s outside wheel must travel farther and spin more quickly than the inside wheel.
The differential helps the vehicle make this imbalanced motion and power distribution by sending more power to one wheel over the other. Instead of a fixed gear system, the differential features a ring and bevel gears that let the wheels rotate independently of one another even though they share an axel. Driven by the engine, the wheels each gain a different amount of power for the duration of the curve or turn.
How Electric Cars Differ
Electric cars use a very different engine than gas-powered or diesel-powered engines, but their wheels still have to turn for curves and turns, so they still use a differential. Besides the engine difference, the transmission also differs. While the typical gas- or diesel-powered vehicle features a manual or automatic transmission of five to nine gears, an electric vehicle only features a single-gear transmission.
An electric vehicle uses a computer-controlled limited-slip differential. Typically located in the center, this E-Differential, as it gets called, or just E-Diff, communicates differently than one for a gas- or diesel-powered vehicle.
The E-Diff uses a combination of three pieces of electronic information to tell the vehicle how to balance power. These three pieces of information come from the:
- steering wheel command signal,
- throttle position signal,
- motor speed signals.
The computer in the vehicle combines this information to tell the wheels which gets the most power and how much, and which gets the least power and how much. Doing this ensures each wheel receives the torque its needs.
Related: Do EVs Have Power Steering?
Benefits of an E-Diff
The design of an E-Diff offers enhanced traction control. This results in improved vehicle performance and response.
An E-Diff will also typically include a locking device that engages when the driver places the vehicle in park. This keeps the gears locked until the driver re-starts the vehicle and moves it into a driving gear option, including reverse.
Repair of E-Diffs
While an e-diff does the same job as a traditional differential, you need to treat it differently when servicing it. Even if you know cars and you would typically repair your own vehicle, an electric vehicle needs to go to the shop for professional repairs.
The vehicles use manufacturer-specific computer software only available to certified mechanics who have attended the manufacturer’s training program. The computer program tells the mechanics about the issue using diagnostic codes. This requires a manufacturer-specific interface, too.
The parts to repair these differentials aren’t commercially available, like those for gas-powered vehicles. You can’t stop by NAPA to pick up the items to repair a troubled electric vehicle differential. It will require professional help.
Each of the manufacturers uses its own design. Motor and batteries only start the list of the many competing parts used in the multitude of designs. Differentials also differ by manufacturer, so the design used by Tesla differs from the one used by Subaru.
Considerations When Shopping for an EV
Keep these factors in mind when you shop for an electric vehicle. If you purchase a used electric vehicle, choose a brand that has a new car auto lot in or near your hometown. Typically, auto sales lots that sell new cars have a repair shop on site with manufacturer-certified technicians and mechanics. You’ll have somewhere nearby to service your vehicle should the differential need repair.
This may mean switching from your traditional mechanic. As heartbreaking as that can be if you’ve gone to the same person for years and built trust, EVs make it necessary. Although you may find a few mechanics who aren’t affiliated with an auto sales lot that obtained the certifications and own the software and cables to examine the vehicle and repair, this rarely occurs. By and large, the manufacturers limit their training to those affiliated with the vehicle sales lots.
