Adding a carbon-fiber QA1 driveshaft not only made this Mustang quicker, but safer, too.

Drag racing physics dictate that it’s easier to accelerate a light car, therefore, improved acceleration can also come from reducing the weight of the vehicle’s parts.

This is especially true of parts that spin, such as the wheels, engine pulleys, flywheels, clutches, and the driveshaft, too. In some cases, finding the performance is easy and the gains can be measured in tenths. Remember: Drag racing physics are your friend.

Though hard to believe, the stock two-piece shaft weighs roughly 40 lbs. There’s quite a difference between the two driveshafts. QA1’s REV carbon fiber unit comes in at just 23.5 lbs.

Example: Most factory driveshafts are made of steel because it’s easy and affordable to manufacture. Swapping to aluminum or carbon fiber will reduce the rotating mass, thus allowing the driveline to be more easily accelerated.

QA1 REV Series carbon fiber driveshafts are available for a variety of vehicles. They are wound in-house using 3M Matrix Resin in QA1’s Lakeville, Minnesota, facility.

The result is often an instant improvement in elapsed time, along with other benefits. This is appealing to street muscle and racing enthusiasts alike, but when you are buying driveshafts by the hundreds of thousands, the OEMs typically take the path of cheaper resistance.

Almost all newer rear-wheel drive cars come equipped with a two-piece driveshaft, regardless of brand. These reduce NVH (noise/vibration/harshness), but carry extra weight, especially when a center bearing and hanger is used.

Driveshaft diameter is important, but it needs to be considered in conjunction with wall thickness and the type of materials used to make the driveshaft. There is a trade off in diameter and wall thickness from a torque and critical speed standpoint. Also, the modulus or stiffness of the material plays a significant role in what diameter is desired. In a composite shaft, fibers can be oriented so that a driveshaft can have a relatively small diameter but maintain a high strength and critical speed.

Another downside is strength, or lack thereof, as two-piece shafts are not the greatest for handling the bite of increased traction and/or increased power. In fact, they can be pushed to the limit in a stock vehicle with just the addition of drag radials on a sticky track.

Thankfully, driveshaft swaps are relatively easy. They are a bolt-in item that can be installed in a driveway or home garage with a floor jack, jack stands and basic tools.

To illustrate the advantages of a one-piece driveshaft, we completed a before-and-after drag test. Our subject is a 2014 Mustang GT, but the theory can be applied to almost any car with a similar driveshaft. All 2005-2014 (S197 chassis), 2015-’23 (S550), and ’24-up (S650) Mustangs come with a steel, two-piece driveshaft. These work nicely to limit NVH, but at 38-40 lbs., they certainly are heavy.

Here’s an example of a driveshaft tested to failure in QA1’s torsion test machine. Rather than twist and snap, carbon fiber driveshafts tend to shred when they fail.

The test subject Mustang sports a VMP supercharger on the 5.0L Coyote engine, it’s backed with a FTI torque converter and runs 10s in the quarter mile. The car is driven thousands of miles per year to Drag-and-Drive events, so durability is important—especially since the owner, Kevin McKenna, doesn’t own a trailer. (Read more about its exploits here.)

Looking for maximum performance in a bolt-in application led us to select a QA1 REV carbon fiber driveshaft that’s designed specifically for late-model Mustangs. They can be ordered with or without SFI certification for roughly a $100 difference.

“Our REV driveshafts are engineered as a system to efficiently connect the transmission to the rear end,” said Dave Goldie Drag Race Product Manager at QA1. “They can handle up to 1,500 horsepower with a max rated torque of 1,000 lb-ft. They feature Spicer Life Series 1350 U-joints and utilize a high-speed CV joint with a high-speed sealing boot and high temp grease. This high-speed capability allows us to minimize effects of NVH while increasing performance.”

As for weight, the 2005-2018 Mustang REV-series carbon fiber driveshaft is just 23.5 lbs., and QA1 offers these as a direct bolt-in for almost any 2005-present Mustang.

The guys at Skillman Ford had a little fun showing the weight difference between the two shafts.

“A single-piece driveshaft can be a significant improvement over the stock two-piece shaft,” said Goldie. “The auto manufacturers have design criteria including length and diameter that make a single-piece driveshaft pretty much impossible using traditional materials. Automotive designers must adhere to constraints like how close the shaft can be to other components, plus driveshaft cost, and of course, they have concern for NVH. This leads them to a two-piece design that is typically heavy and may include rubber mounting or drive components. In the aftermarket/racing world, these restrictions do not exist and allow the use of larger diameters and alternate materials such as carbon fiber,” Goldie said.

Speed Is Critical

When designing a single-piece driveshaft for newer production vehicles, a major concern is the critical speed of the driveshaft. This is due to the ever-decreasing area around a driveshaft that would allow for a larger diameter. Since diameter is relatively limited, composites are a good solution for higher critical speed encountered in racing and offer a significant weight savings over traditional materials.

“A one-piece composite design can save as much as 20 pounds over the stock assembly. Carbon fiber is preferred because it’s the safest and lightest material available to the racing world. Most of us have seen the damage that a steel or aluminum driveshaft can do to the cockpit of a race car,” explained Goldie. “In the unlikely event of a failure, a carbon fiber driveshaft shreds like a broom, so there is no damage to the racer or other parts of the car.”

To ensure the highest standards, QA1 builds its carbon fiber driveshafts in house.

“This is a necessary process to design and produce the correct torsional stiffness specifications for world-class carbon fiber driveshafts. It is imperative to have control over the entire filament winding process, and by having the specialized equipment in-house, QA1 can customize tube length, wall thickness and pattern, enabling products such as carbon fiber driveshafts to be designed and wound for specific applications. QA1 designs, engineers and manufactures unique composite components, enabling the customization of tube dimensions for customer requirements,” said Goldie.

Install and Test

Ray Skillman Ford in Greenwood, Indiana handled the job in a couple of hours. After hoisting the vehicle, it involves removing the exhaust and unbolting and replacing the shaft. At time of installation, the owner also installed a Stifflers driveshaft safety loop to make the car legal for NHRA competition. After installation, everything was inspected in the area around the driveshaft to ensure proper clearance. Carbon fiber is very strong, but it can be damaged easily should it contact components while spinning.

With the new parts installed, Kevin headed to Wild Wednesday at Lucas Oil Raceway at Indianapolis. In addition to working for NHRA, Kevin is a two-time champion in NMRA HP Tuners Super Stang, so he can hustle a car down track.

The Mustang was previously run in Florida, where it produced a best E.T. of 10.79 at 126 mph. But this was summer in Indy at Lucas Oil Raceway (which sits at 856 feet) and corrected altitude during out test was 2,900 ASL. In these conditions McKenna had been running in the 11.09-11.15 range.

“I’m very pleased,” said McKenna after making three runs. “The car ran 11.04, 11.02 and after a nice cooldown it went 10.99 at 128.45 mph in conditions that were less than favorable, compared to the cool, seal-level conditions in Florida (1,300 feet corrected). Based on similar runs, I’d estimate that the driveshaft was worth every bit of 0.090-to-.020-second on average. Best of all, the car was noticeably smoother, which makes me wonder if the stock driveshaft was slightly out of balance or perhaps the QA1 unit is just that darned good.”

This proves once again the drag racing physics can be your friend.