What rear end does my truck have?

[Gr8bawana]

I just bought a 2017 4x4 SLT 2500 CTD and it has an open diff in the rear end. How do I find out what Limited-slip I can have installed and still keep the 3.42 gears?

 

[crash68]

The truck has an 11.5" AAM rear axle, you might as well go with a Detroit TrueTrac limited slip.
Even the factory limited slip is a helical-gear limited slip.