SRT® Hallmarks: A true mechanical limited-slip differential.

Performance. Plain and simple. That's the deciding factor when SRT designers and engineers are working their magic in the studio and lab.
Posted on Oct 11, 2012

Performance. Plain and simple. That's the deciding factor when SRT® designers and engineers are working their magic in the studio and lab. With the 2012 Charger SRT, 300 SRT and Challenger SRT, it was a natural fit to utilize a true mechanical limited-slip differential to harness all of that power. After all, each features a 6.4-liter 392 cubic-inch HEMI® that churns out 470 horsepower.

SRT partnered with Getrag to produce a mechanical limited-slip differential that was first introduced on 2010 models. The limited-slip differential on SRT models (Charger, 300, Challenger) has a torque ratio of 1.8, which reduces the amount of clutch slip between each side of the axle.

The Getrag is a torque-sensing system, whereby the speed of the inner wheel versus the outer wheel speed is found, then modulated to make the pair equal via the clutches and the differentials. This allows for a relatively small difference in rotation while cornering, and helps prevent excessive wheelspin that could lead to a loss of traction.

"We knew right up front that we were developing a more 'torquey' horsepower-friendly engine, so we made sure this axle from Getrag would have the capability to hold that kind of torque," said Marty Jagoda, Vehicle Integration Responsible, Chrysler 300 SRT/Charger SRT. "The reason we moved from an open differential to a limited-slip differential is purely performance."

Charger, 300 and Challenger SRT models have two modes (three for 2013 models) of electronic stability control (ESC) that work in conjunction with the limited-slip differential. The first "Auto," or full-on, which is the system that operates each time the vehicle is started. This mode mitigates torque in heavy acceleration situations to help keep car control. The second mode, "Sport," turns the traction control off and gives the driver an enhanced operating limit. The third mode, "Track," turns the ESC system completely off, though maintaining ABS functionality.

Working in conjunction with the mechanical, limited-slip differential is brake-locking differential technology used in extreme circumstances. For example, if the vehicle is extremely out of shape, or if there is an over-temp of the axle fluid that causes the clutch to slip, the brake-locking differential will make sure the vehicle stays in control and both rear wheels are of equal speed.

"We know it's cool to say a limited-slip diff versus an open diff, but at SRT we don't do anything to be cool or uncool," said Jagoda. "It's solely driven by the performance of the vehicle and what the vehicle wants. Our vehicles demand a true mechanical limited-slip differential, which they now have."

Even distribution of the power to the pavement thanks to a limited-slip differential, that's another of the many performance benefits of driving an SRT product.

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