In an effort to make the 2015 Mustang GT a global car, Ford put an IRS under the car. The IRS is designed to offer an improved, more controlled ride over that of a solid-axle rear end. Many of the European and Japanese performance vehicles come with an IRS, which made the outgoing Mustang seem outdated in many eyes.
Thing is, we don’t know of any true Mustang enthusiasts that ever wanted the Mustang to have an IRS. It was the non-Mustang press that would harp on Ford for the Mustang coming with an “archaic” solid axle arrangement. Ford’s first attempt to quiet the critics was with ’99, ’01, and ’03-’04 Cobras, and what was the first thing we did with those cars?! We either swapped out the factory half shafts for performance versions, or we replaced the whole IRS for a solid axle rear. We’re sure Blow-By Racing, who did the half shaft swap here, performed many a solid axle swap, and probably still does.
The majority of Mustang enthusiasts didn’t like the IRS when it appeared in previous Mustangs, but it was easy to get around it. We could either not buy a Cobra, or it was a pretty easy fix to swap in a solid-axle since the chassis was unchanged between the IRS and solid-axle Mustangs. That is not the case with the ’15 model. Thankfully, in the eyes of Mustang followers, Ford went away from the IRS in the S197 years, but now it’s back.
Now what? If we want a new Mustang, we don’t have a choice now; it’s either have an IRS, or not have a new Mustang. Well, it’s back to swapping out the factory half shafts for performance versions. Thankfully, Blow-By Racing and the Driveshaft Shop has seen this movie before so both know the cure for the half shaft blues. Both know the answer is stronger half shafts, of course.
When to Add Aftermarket Half Shafts
First off, no one really knows the horsepower limit of the factory half shafts. Many believe they are much stronger than what was on the aforementioned Cobras. Your ’15 GT’s half shafts may last under the abuse of 600-rwhp, and someone else’s may break with the stock engine. However, one thing we do know; if your Mustang is going to be a regular at the drag strip with any kind of sticky tire under it, the stock half shafts are living on borrowed time.
Driveshaft Shop 800HP Direct-Fit Axles
The Driveshaft Shop (DSS) made its name in the last decade with its upgraded Cobra axles, so we aren’t surprised that it was one of the first companies to market with improved axles. DSS acknowledges the fact that the ’15 Mustang GT half shafts are better than the earlier cars, but believes its product is still an improvement.
DSS’ 800HP Direct-Fit axles, which is what Blow-By is installing here, features a material called Ovaco 300, developed by Ovaco Steel out of Sweden. Each spline is made from this Ovaco 300 steel with 4340 billet CV mounts, the company’s proven 108mm CV with full 300m billet chromoly cages and races, NEO HPCC1 grease, and a high-durometer Neoprene boot. “It will handle just about anything you can put to it,” DSS says. DSS’ 800HP Direct-Fit axles have an MSRP of $1,200 a pair, and the company has 1,400HP versions, as well, that use 30-spline bars.
DSS’ 800HP Direct-Fit axles are ideal for bolt-on, power adder ’15 Mustang GTs, but with a built engine, and more aggressive power adder, a step up to the 1,400HP Direct-Fit axles would be in order. For Blow-By’s test car, the car doesn’t have a power adder, as of yet, but the car is exercised in a vigorous manner on a regular basis so the DSS axles serve as mechanical insurance against imminent failure.