what t-case is in the truck now top shift/forward shift 21 or 23 spline your old top shift case is a 21 spline so if your current case is 21 spline your good to go, you need to get marlins mco7,mco8 or mco8r10 in a 21 spline and there crossmember they come with directions but heres what you do in a nut shell which ever t-case matches up to your tranny is going to be your crawl box if your trans accepts top shift use a top shift for the front case if the trans accepts forward shift then use a forward shift, you tear down that t-case untell its just the reduction housing the front part then the adapter bolts to the back of that then a compleate top shift t-case bolts to the adapter the same way it would to the back of the tranny then the whole assembily bolts to the tranny
