Let’s start by understanding how a simple “open” differential works. The order of power distribution to the wheels starts at the pinion, which sends torque from the driveshaft to something called the ring gear. Inside the differential housing, you’ll notice that the ring gear is connected to the spider gear(s), which turn the respective side gears and in turn transmit power to the rear wheels. This arrangement allows the wheels to spin at different speeds, making it easier for the car to execute a turn.
In addition to that ‘basic’ differential, there are different versions of differentials, including locking differentials and locking differentials, that can control the power supply to the wheels. And some have electronics to change their behavior.
As you may know, a limited slip differential, or LSD, is more complex than an open differential. In addition to the basic differential, LSDs have several friction discs and steel plates, i.e. clutch packs, within the housing to control wheel speed. But while a purely mechanical LSD relies on gear geometry and friction, an electronic limited slip differential (eLSD) ensures that the clutch is controlled externally via actuators and software.
As the name suggests, limited slip differentials can be mechanically “locked” to ensure even power delivery to both wheels. This can be controlled manually or automatically, based on the available traction. But with the electronics in, like you’ll find in a heavy-duty Chevy Silverado ZR2, an electronically controlled solenoid/motor engages the lock gears, eliminating the differential’s ability to independently control wheel speed. These differences are also called “e-lockers”.
Electronic differentials are superior, but not always
Both mechanical and electronic systems have many advantages and disadvantages. For example, the simplicity of the mechanical differential makes it a more cost-effective and reliable choice than electronically controlled systems. A fairly simple differential setup tends to be more predictable, especially in extreme off-road conditions. That said, mechanical lockers (also called automatic lockers) are known for their sporadic and inconsistent engagement, which may not help.
It’s also worth pointing out that diagnosing and repairing a simple mechanical differential is much less complicated than with an e-diff. Since the latter comes with several sensors and control modules, troubleshooting won’t be easy, and there’s a good chance you’ll encounter calibration issues if you try to use it.
However, there are advantages to using an electronic system. Take the case of an eLSD. The system responds much faster and adapts to external conditions. Although the differential has notable shortcomings, it provides extra precision and improved control.
The 992 Porsche 911 GT3 RS, for example, gets a handy electronic rear differential with different settings for coasting and acceleration lock. Without delving too far into the weeds, the e-diff allows you to better tailor the oversteer and understeer characteristics of the sports car to your driving style or the circuit itself. Not all tracks – or roads for that matter – are equal; some have trickier angles and curves than others.
Mind you, that’s next-level platinum hardware for a six-figure sports car. For mere mortals, the response time of an eLSD versus a regular mechanical LSD won’t be that noticeable, at least not on dry asphalt.
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