Review & Install Video
Hey guys, Stephanie with AmericanMuscle.com here with this Ford Racing LSD for 31 spline 8.8 rears, or to break it down, 86 to 14 V8s and 2011 to 2014 V6 Mustangs. This Posi unit from Ford Racing is going to be a good option for the guys out there with an 8.8 rear that are looking to replace their diff with the next upgrade over stock. This diff has carbon discs and requires the use of 31 spline axles, which gives it that upgrade over the factory components. And if you're planning on or already have some bigger power and torque numbers from your 'stang, or the car sees some track time or hard launches, a differential upgrade should be something that you're looking into.
There are a couple of reasons to change or upgrade your differential. Maybe you've got a stock diff and it's just getting old or chattering, or maybe you plan on hitting the drag strip and you've got some power that you'd like to cleanly get to the ground. Either way, this Ford Racing diff would be a good option, because it's got a balance of being an upgraded part that can handle more power and torque, but that isn't such an upgrade that it wouldn't make sense for a completely stock car to upgrade to. This diff is actually the same diff that came from the factory in the O3 to O4 Cobras, so it's a beefed up version of a factory style diff if you have any other Mustang besides the O3 to O4 Cobra.
Like I mentioned earlier, this diff is going to require the use of 31 spline axles, so if you've got an O4 and under V8, you're looking at upgrading your axles, since those cars came from the factory with 28 spline axles. If you've got an O5 and up you can reuse your factory axles with this diff, but you're still looking at an upgrade due to the fact that this diff has carbon discs. The carbon fiber discs that I keep referencing refers to the clutch pack. This diff uses the same carbon fiber clutch pack that's used in the Cobra and Shelby SVTs, and the carbon friction plates are much more durable and they're designed for a higher torque than the stock friction plates are.
If we take a step back for a minute, the point of a limited slip differential, or an LSD like this one here, is to allow both rear wheels to put power to the ground and give better traction to both rear wheels. So the thought is, if there's any type of open diff transfer or uneven transfer of power and torque to one particular wheel over the other, that'll create a useless wheel spin where the car loses its forward momentum, the LSD is designed to eliminate that spin. It'll transfer the torque of both wheels evenly and will have a few benefits in both street and track applications. This means a stable differential lock pattern that won't fail due to the upgraded components, and no slipping, more durability, gentle transitions, and even a quiet operation.
This is going to work for cars with both solid axle and IRS, or independent rear suspension, and you'll need to reuse yours or grab a new 8.8 rear set since this diff will not come with aftermarket rear gears. One other note would be the recommended use of 75W90 rear gear oil, since those will give you the same oil weight as the factory, and you're going to need three quarts of that and four ounces of friction modifier for the initial fill. When it comes to the price, this rear diff is going to cost $230, and it's going to be the most wallet friendly option on the site when it comes to LSDs. There are some beefier options on the site if you really need to upgrade for power reasons, but those are obviously more expensive, and it's nice to see an upgrade over the factory components from Ford Racing that you aren't going to have to turn the red light on for.
As for the install, you're going to need some experience for this one. You'll need a few different wrenches and sockets, but an impact gun is going to help you speed things up here, even though you can do this install with all manual tools if you wish. A lift would also really help, and you're going to need a torque wrench to do this properly. You're looking at about four hours' time and a three out of three wrenches on the difficulty meter. You're going to need to get to the diff itself, so this means pulling the rear wheels, dropping the rear brake assemblies, draining and removing the rear diff covers, so you will need something to drain into. Once you have the diff uncovered, this is where the benefit of mechanical knowledge will come in.
You'll need to rotate the axles until the diff pin retaining bolt is accessible, because you'll need to get this pin out so you can push the rear axles out of the diff. Once those are out, you're looking at backing out the diff-bearing cat bolts and pulling the diff out of the car. You need to reinstall the shims that are on each side of the diff bearings the exact same way that they came out, so keep track of those. The new diff bearings will need to be pressed onto each side of the new diff and you can reuse the ring gear off of the old diff. And after that, it's just a matter of reinstalling things. Reinstall the shims, reinstall the diff and the retaining pin, the axles, and the housing cover as well. Now, this is obviously a quick overview of the install, but I wanted to give you guys an idea of what it would take so you can make a decision as to whether or not you're going to install this yourself, or you're going to take it to a shop.
Wrapping things up here, the Ford Racing LSD with carbon discs is to be used in 8.8 rears and with 31 spline axles. It's an upgrade over the factory diff unless you have an O3 to O4 Cobra, and in that case, it's an exact replacement. This diff is a good option for those looking for a maintenance replacement, or those looking for something to make sure that they get some extra torque planted squarely to the ground. And you can check it out some more right here at AmericanMuscle.com.