Here are the two ends of the...
Here are the two ends of the UPR lower control arms. The arms offer solid mounting, and the front side of the bar features an adjustable Heim joint. We set the lower control arms to the same length as the Southside bars.
Adding a good suspension system is useless without the inclusion of sticky rear tires. The suspension can work perfectly, but if the tires don't grip the ground, then performance will suffer greatly. Adding a set of sticky meats can and will exploit the weakest link inside the rear. We have a pair of 275/60-15 Mickey Thompson drag radials--a.k.a. rear breakers--under the car right now. Our inventory also includes a pair of M/T ET Street 28x12.50 (measuring 10.5 inches wide) DOT tires mounted on another set of wheels for track use. Just bolting on the radial tires made us think twice about the differential and axles. Our old combo used a set of M/T ET Drag 26x10 slicks--far smaller than our new tire line up. The coupe always spun a little out of the gate, sparing the puny 28-spline axles and traction-lock differential.
Our subject LX has survived some 10-second runs and countless 11-second performances over several years with its stock axles. The differential was replaced once, but with a regular Traction-Lok, nothing special. We attribute its lifespan to the fact that the car is equipped with an AOD transmission, sans transbrake. The very nature of the numerically low First gear of the transmission (2.40:1), coupled with a mild 3,200-rpm stall speed, meant this coupe left lightly compared to its stick-shift brethren. That was about to change due to the forthcoming powerplant upgrade.
These aluminum sleeves are...
These aluminum sleeves are inserted on the Heim-joint ends. The UPR XD-series feature tool-steel sleeves for extreme drag-racing duty.
Unlike the late-model GM F-body cars, the Mustang was built with a stout rearend housing. A few simple mods are all that is required to get the Ford 8.8-inch rear strengthened. Larger axles and a tough differential go a long way in the Mustang world. We tapped Latemodel Restoration for its five-lug conversion kit. Since we wanted to add 31-spline axles, it was a good time to increase our lug count from four to five. Adding five lugs opens up the choice of wheels on the market for both track and street use. Plus, the lug strength is increased due to distributing the load to five lugs, as opposed to four. We have seen the lugs sheer off on quite a few 10-second cars, so we wanted to avoid that unpleasant experience.
A quick phone call to Summit Racing netted us an Eaton Detroit Locker differential to fit the 31-spline axles. The Detroit Locker diff is a nasty unit that is more than capable of handling 9- and 10-second runs, but it still has limited-slip capabilities for subtle street manners. The same 3.73 gears were re-installed in the rear, but only after a thorough inspection. Miraculously, after 15 years of use, the gears looked great without any hint of wear. We saved money by reusing the gears, but still added new shims and bearings that we bought from the local NAPA store.
The lower control arms bolt...
The lower control arms bolt in easily. Factory mounting holes have to be drilled out to accept the new -inch hardware from UPR. The stock arms are bolted in using 12mm hardware.
The modifications took about a day with two DMC techs working on our coupe. The process required a little cutting and welding in order to install the UPR adjustable spring perches on the body. Your author found an old set of five-lug Weld Draglite wheels in the basement for the car. The wheels added that classic and timeless 5.0L look to our coupe.
The new rear-suspension setup complements our recent front-suspension overhaul that included a tubular K-member and A-arm setup, along with coilover struts. The front-end mods removed 67 pounds, including the skinnies. The reduced weight will help weight transfer and let the rear suspension work even better in planting the variety of DOT tires we have for this car. Thanks to UPR, Strange Engineering, Latemodel Restoration, Royal Purple, Mickey Thompson, and Summit Racing, we have brought back the bite to go along with the supercharged bark under the hood.
Here is A comparison of the...
Here is A comparison of the stock upper control arm (right) and the UPR Pro-Series upper arm. Adjustability and strength are the key components to our new control arms. UPR also offers upper and lower control-arm-mount reinforcements for those cars with damaged torque boxes. Our car was fine, but we've seen heavy damage in vehicles that log serious miles on the dragstrip, especially stick-shift applications.
The factory bushings were...
The factory bushings were wore out, cracked, and unreliable.
The stock (right) versus the...
The stock (right) versus the spherical bearing.
The bearing is installed on...
The bearing is installed on the rearend housing, and the control arms bolt-in easily.
According to Martorella, pinion...
According to Martorella, pinion angle should be set at -1 or -2 degrees for most applications. He said the UPR upper control arms can be adjusted without removing it, making it easy to compensate for different size tires and lowered cars. Adjust pinion angle when the car is level on the ground or a drive-on lift.
Ride height is a critical...
Ride height is a critical aspect of performance. Lower cars cut the air better, but that affects the body's ability to roll back on to the rear tires at launch. Adjustable spring perches are welded to the chassis, and the ring is used to set ride height.
The stock spring cup is cut...
The stock spring cup is cut out.
Rondeau welded the new unit...
Rondeau welded the new unit in place.
The spring is squeezed into...
The spring is squeezed into place. It might look goofy: The spring is bent and the bottom is half on the perch when the suspension is fully extended. Once the car is on the ground, the spring sits normally. Double check the top and bottom of the coil to ensure the spring is sitting solidly on the perches in a post-install inspection.
Here's The stock rear shock...
Here's The stock rear shock (left) and the new adjustable Strange shock.
The knob at the bottom of...
The knob at the bottom of the shock is used to adjust the stiffness and looseness of its rebound. The looser the shock, the harder the car will hit the tires. There are ten settings on these shocks. Full loose is when the knob is turned counter-clockwise.
Strange shocks are direct...
Strange shocks are direct bolt-in items.
Our cheap exhaust system of...
Our cheap exhaust system of unknown origins blocked us from installing an antiroll bar. The bend over the axle interfered with the mount.
A set of turndowns is in the...
A set of turndowns is in the future for this car; the antiroll bar will be put in at that time.
Differential fluid smells--badly--after...
Differential fluid smells--badly--after many years of use. We popped off the diff cover and drained the old fluid.
Once the old differential...
Once the old differential was removed, we unbolted the ring gear and inspected it. It's hard to believe, but after 15 years of use, the ring and pinion gears looked perfect. Neither gear showed any signs of wear.
New bearings were pressed...
New bearings were pressed on the Detroit Locker differential.
The ring gear was bolted on...
The ring gear was bolted on and torqued to 70 ft-lb. The caps holding in the differential are torqued into place with 70-85 ft-lb of force.