Originally Posted by RedBird2
For 2012 / 2013. There is a trailer tow package and then there is a max tow package. Only the max tow package includes the 3.73. However some dealers order the trailer tow package and the 3.73 as separate items. Costs an extra 100 to do so for 2013.
If you have stock wheel and tires and hit ~2300 rpm @ 70 MPH then you likely have the 3.73.
In 2010 if you ordered the "Max Tow package" it would force the change on the build sheet to 3.73. If the vehicle build already had 3.73's then you could chose the "Tow Package" and add just that. Either way, if it had a towing package it would have 3.73's almost every time except.... If it had 4.10's you also would just add the "tow Package" to complete it.
This is the way I have seen it explained.
Either one would be 3.73's, 4 prong wiring, 2" receiver and the sway control program.
Mine appears to have been ordered as 3.73's with Auto transmission and then "Tow Package" was added to complete the set. My build sheet list them that way. And later in the list the Limited slip rear shows up as well.
But I found all this for certain by going to the Owners site, creating a profile with the VIN number and then I could see the original build configuration and options.