I have a 2003 Chevrolet Suburban 5.3L 4WD.Question:  How do I find out what size front differential it has.Answer:  Your front differential is a  8.25 IFS.  You can see the front differential carriers assemblies we offer on our site.  If you only need a ring and pinion and or bearing overhaul kit give Scott a call 888-824-2012 he can help you.