The battle has been waged for decades—full-frame or unibody? Unibody chassis are lightweight, which makes them a no-brainer for performance, but that lightweight design comes at a cost. Stability in a unibody is less than optimum, hence the need for things like subframe connectors and stiffening bars, where the 79-04 Mustang is no exception in this area. While they are well known for being easy 9-second candidates, to get there you need some suspension work. One key weak spot are the rear torque boxes, which is why we turned to Wild Rides for our Project 666 Fox body Mustang.
Launching on slicks or even drag radials puts an incredible amount of stress on the factory torque box, more than what it was designed for. Eventually, the cracks appear in the fatigued sheet metal and the mounting holes stretch out. Initial signs of torque box damage include separation of the metal panels, broken welds, and distorted sheet metal.
The Advantages of the Wild Rides S-Box
Both upper and lower torque boxes can (and should) be reinforced before bolting on a set of slicks. If your car has already been thrashed at the track, that is OK, the Wild Rides S-box components will repair the damage and prevent it from happening again. In addition to the bulletproof design, the Wild Rides S-box also gives you adjustability; with 3 control arm mounting holes, you can change the instant center of the rear suspension to match your engine/transmission combination.
When paired with the upper S-box kit, you get the same adjustment potential as a true 4-link, while utilizing the stock suspension components for stock classes. “When asked, ‘do I need both the Upper S-Box & Lower S-Box’, the answer will vary depending on how much power and what some ones intentions are with the car,” said Gene Giroud of Wild Rides. “Both boxes give you more structure and adjustability.”
One look under 666 and you will see that it has been beat on. The factory torque boxes have been welded up; each seam fully welded to the body. If you cruise the forums, you will find that one of the most common solutions to the stock torque box problem is to weld up all the seams. Some of the Fox-body “forum experts” suggest seam welding on any car that has not seen any damage; that the welding is good enough.
The basis for a consistent drag car is to have a good stiff chassis.
Prepping for Disassembly
There are a few key areas that you need to address before you start any disassembly. If the stock boxes are in good shape, you should make some reference measurements to ensure the new S-boxes are in the correct locations. This is done by pulling a string across the bottom of the frame rails, even with forward edge of the two 1-inch holes to about 10-inches back from the rear edge of the control arm mount hole in the torque box. Secure the string in position. Next, measure the center of the control arm mounting hole to the string on both sides. This will give you your factory reference point. The same procedure will be used to verify the new S-box location once it is set in position.
Disassembly and Installation
While installing Wild Ride’s S-boxes is not super complicated, it is not a bolt-in procedure. You have cut, grind and weld many of the components in precise locations in order for everything to be square and correct. That means that if your welding skills are not up to the task (would you bet your life and the lives of others around you on them), then get some help from someone who is an experienced welder. By taking your time, checking and re-checking the fit, the end result will provide a serious advantage of an otherwise stock chassis Mustang. Though the advantages of this cost-effective piece will pay off in the long haul, helping us reduce chassis flex and adding adjustability!