I have 4.10's with my AOD and just used the white 23 tooth gear. Its not perfect, but a lot closer than the stock tan gear was. If all else fails, you could contact a local speedometer shop and have them make a gear reduction box for you. They will want you to mark your milage and drive exactly 5 miles then mark it again. From there they will make you a box that splices into your speedometer cable and corrects the speedo. I priced one and they wanted 100.00.