28/31 spline??

[~The Jester~]

If your counting the splines on the pinion gear itself, you should be fine. Those splines are what the driveshaft yolk slip on to.

Now if you bought the whole carrier, and you're counting the splines on the side gears, this is where the axles spline count comes into play. Your Stang came with 28 spline axles, not 31. Not a big deal, many options here. Like was mentioned before, simply swap the new ring gear onto your carrier, and presto. Or, Strange, Mosier, and a few others make 31 spline axles that slide right in. They're stronger than stock, and almost bulletproof. Good time to upgrade if this is the problem you're having.