Camaro 2010-2013, 1LE 3.91 Gear Kit, GM # 19301504 

GEAR SET - GM (19329768) Extemely Limited Availablilty.

If you want the ultimate acceleration off the line, look no further than this shorter gear ratio. This ring and pinion comes out of the 1LE, and the higher numeric ratio gives your fifth-gen Camaro a dramatic increase in acceleration. The drive gear increases effective rear-wheel torque multiplication by 13 percent in a manual-transmission Camaro SS, and a whopping 20 percent in automatic cars.
The complete 3.91 Performance Gear Kit includes the ring and pinion, all hardware, shims, gaskets, oil additive, and instructions (included, not shown). The 3.91 gear installation requires recalibration, which is installed by a GM dealer. Application for a CARB E.O. has been made at the time of this writing.

Gen 5 Camaro 1LE 3.91 Gear Kit
This lower (higher numerically) ratio rear drive gear kit will increase effective rear wheel torque multiplication in Gen 5 Camaros by 13% (over standard 3.45 ratio) in a manual transmission-equipped car, and 20% (over standard 3.27 ratio) in an automatic-equipped car. This gearset is the original equipment ratio found in the 2013 – 2015 1LE Camaro package. Reflash of the speedometer calibration by your dealer is included with the kit. GM provides a calibration and new certification label.
The kit includes:
22813040 (1) Gear Kit
92230403 (1) Gasket
92230584 (1) Oil Seal
90538867 (3) Nut
92138569 (3) Bolt
92139104 (3) Bolt
88900330 (1) Limited-Slip Differential Oil Additive
19301909 (1) Label Altered Vehicle Cert.
19301503 (1) Instruction Sheet