Heres a little info from the site
http://www.powertrax.com
In some vehicles, you will hear a light clicking noise as the gears are overrunning themselves and allowing the wheels to differentiate in a turn. This is normal of most lockers on the market today. We recommend the Lock-Right for vehicles that are primarily driven in severe driving conditions or are used for recreational off-road. For vehicles that are driven daily or require more mainstream application, the Powertrax No-Slip Traction System offers a quieter and smoother performance.