Originally Posted by CHVYKLR
you're right. that's new. the Ram site lets you select anti-spin differential with the 3.55s or 3.92s but it is removed if you select the 3.21s.
The 3.21's use a different housing and therefore cannot accept the LSD carrier (I looked into upgrading my 2009 w/ 3.21's). LSD is an option (and upgradable) for 3.55, 3.92 and 4.10 gears. I can't remember what it was going to cost though. I stopped listening when the bill got to more than $2500 to change my 3.21's over.