Look on the axle tube next to the differential, or possibly on the tag attached by one of the diff cover bolts, there should be a 6 digit number. Go to dana's website I belive it is danaexpert.com (do a google to be sure) and go to the BOM lookup and enter that number. It will give you some basic info on your axle. Also you can call Randy's ring and Pinion tech help and they can help you out.