51Gib, the 2.56 gear was fairly standard in most GM cars with Auto trans. Most 10 bolt axles had either 2.56 or 2.73, the problem is when you decide to change to a deeper gear you need 3.08 or lower, you need to change the carrier as well. I ran into this with my 10 bolt. I found a ring gear spacer that allows me to keep the carrier and change the gears. It took some searching around but they are out there. GM made the 10 bolt with an 8.2 and 8.5 , the 8.5 is the stronger of the 2 carriers so be sure what your looking at. As a note the 10 bolt for a Pontiac was completely different and the carrier will not interchange with other GM's
