The Axle Exchange driveshaft...
The Axle Exchange driveshaft is a simple swap that goes in without any modifications.
To keep it all honest, we kept the street tune in the PCM for the after-testing with the TCI torque converter and Axle Exchange driveshaft. We ventured to Atco Raceway to get some on-track results. The gains were instantly realized as our GT ran 11.31 at 120.04 mph. That was a 0.27-second improvement over our previous best of 11.58 with reduced timing. The mph was similar, but the time was quicker thanks to a better 60-foot. The 11.58 came by way of a 1.71, and the 11.31 featured a 1.57 short time.
The 11.31 wasn't enough, so we plugged in the DiabloSport Trinity hand-held tuner and added a degree of timing through the entire curve, bringing it to 17 degrees at 6,500 rpm. Our car dug in, rocketed through the 60-foot clocks with the same 1.57, and made it to the finish line with a new best of 11.24 at 120.62 mph. Not bad for a car we drove to the track, swapped the tires, and only cooled down by opening the hood. On the street, the car is an animal, and the only difference is that the torque converter feels slightly looser.
The slip yoke (the accordion-looking...
The slip yoke (the accordion-looking piece) goes toward the front side, whereas some other aftermarket driveshafts have it on the backside. So be warned that your friend's driveshaft might be installed differently than the Axle Exchange unit.
Now we're thinking-with low 11s so easy, what would it take to run 10s?
RPM/MPH Formula
MPH x Rear Gear x 336 (constant) / Tire Height
For Example:
119 x 4.10 x 336 / 26.0 = 6,305 rpm
On track and at 119 mph, the rpm will be screaming at 6,305 since we run on 26-inch-tall ET Street DOT tires. Given tire growth, the rpm will probably be a little lower, but we don't have an accurate way of accounting for it. Radials won't grow like bias-ply meats, so that factors into finish-line rpm as well. According to Burcham, ideally you want to select a gear ratio that will rev the engine no more than 500 rpm past your peak horsepower. If the finish-line rpm is above 500 rpm, then a numerically lower rear gear is needed or a switch to taller tires, which effectively changes the gear ratio. Burcham also suggested that if you are crossing the stripe and the engine is below peak hp rpm, then its time to add a more rear gear.
To calculate highway cruising speeds in Overdrive, simply take the trans Overdrive ratio and multiply it by the formula's result. In our case, a 70-mph cruising speed combined with the street-tire height of 25.9 inches gives us an engine speed of 3,723 rpm. The 5R55S has a 0.71:1 Overdrive gear, so it would knock the cruising rpm down to 2,643 rpm (3,723 x 0.71).
Axle Exchange includes a pinion...
Axle Exchange includes a pinion flange in all '05-'10 Mustang kits. The company was quick to tell us that it's a flange and not an adapter plate.
We turned to Mickey Thompson...
We turned to Mickey Thompson ET Street tires for this test. The DOT-legal meats are of the bias-ply design and check in at 26x11.50-17. They are mounted on factory Bullitt wheels.
A healthy burnout is required,...
A healthy burnout is required, and tire pressure worked best when set at 15 psi. Your quickest elapsed time will come when you run as much tire pressure as possible without sacrificing traction. This will cut down on rolling resistance and make for a smoother ride on the top end. We tried 16 psi and spun, so we dropped it down to 15 psi and carded three 1.57 60-foot times in a row. That's with 100-percent bone-stock suspension.