I've been hearing some say they have a 9" and some say they have an 8.8.

I'm not a ford guy, but my Explorer has an 8.8.

What's the difference between them and if looking to install behind some power, which is the better option?

 

Most consider the 9 inch to be the ultimate car rear end. It has a larger ring gear, 3 pinion bearings, and the pinion centerline is offset farther below the ring gear centerline than any other car rear end that I know of. All of this makes it one of the strongest rear ends that you can put in your car. It's also easier to modify the housing to fit many different types of car or truck because the housing is all steel, so you can weld on any part of it. On the down side, it also has more parts in it and it takes more power to turn than the other car rear ends. It's more expensive to build a 9 inch if you are using all new parts.


The 8.8 is a very close copy of the Chevy 12 bolt. They both have almost the same size ring gear, use the same bearings on the pinion and differential, are about the same weight and use the same amount of power. They are also about the same strength. Many of the 8.8 rear ends came with 28 spline axles, but many came with 31 spline axles. The 12 bolt has 30 spline axles. The down side is that it cant take quite as much power as the 9 inch if they are both built comparable, and the center of the housing is cast iron, which limits the amount of welding that you can do to the housing.