Crazy Don Helsel makes an...
Crazy Don Helsel makes an adjustment on the UPR Products '79-'04 Mustang rearend locator (PN 2013; $299.99) he's installing on Rich Bach's Drag Radial Mustang. The 4130 chrome-moly, CNC-machined wishbone is being installed in Rich's Pony in an effort to maintain the rearend's positioning under the force that the 'Stang's nitrous-snorting 427 Windsor throws on 275/60-15 drag radials.
While our normal practice here in Tech Inspection is to focus on products that are primarily geared toward street-driven Mustangs, this month's main attraction-UPR Products' rearend locator (known by racers as a "wishbone") for '79-'04 Mustangs-is a bit more track-specific than our usual subject matter, but we're making light of it here nonetheless, because for many of us the quarter-mile is like a second home for our Ponies.
Those of you with 'Stangs running in the 10-second-and-quicker/120-mph-and-faster range at the dragstrip are probably all-too familiar with the unnerving swish-swash, tail-wagging sensation that you sometimes feel in the seat of your pants when the car is barreling down on the big end on 8-, 9-, or 10.5-inch slicks or drag radials. The dancing-rearend phenomenon is usually caused by a differential housing that is actually moving from side to side as the car accelerates (despite a rollcage, subframe connectors and antiroll bar to help stabilize the chassis).
Any chassis specialist worth...
Any chassis specialist worth his salt will confirm that the key to strength and structural integrity, especially for a Fox-body or SN-95/New Edge Mustang, is through triangulating the braces, bars, and arms that are used to tie the chassis together wherever possible. With its 25.5 SFI certification (legal for 7.50-and-quicker e.t.'s), Rich's '90 has plenty of three-point rigidity in its chassis structure. However, since Rich competes in Drag Radial classes that require stock-style rear suspensions, he is unable to "go all the way" with the Pony's understructure and add a traditional four-link. UPR's wishbone will mount to the frame and the underside of the 'Stang's 8.8 rearend housing (the brace is applicable for 9-inch rears, too), creating a triangular support that does not compromise the stock-style gear in the rear, but will eliminate flexing or bending in the rear section of the chassis.
Yes, boys, horsepower really will do that to a Mustang, and driving through it, which sometimes seems more like simply holding on and praying that disaster doesn't strike, has long been the only way to deal with the situation. That's because a fix used to require the serious expense of stepping up to additional suspension upgrades, such as torque arm/Panhard bar setups, which actually are better-suited to road-race applications.
A rearend-centering wishbone is another alternative for stabilizing drag 'Stangs. The triangular-shaped, tubular device, which attaches to a vehicle's rear framerails and then comes together in a common point below the center of the differential, basically locks a rearend housing in place and prevents sideways movement. The brace actually helps improve a Pony's consistency on the 1,320 as well.
Mounting brackets for the...
Mounting brackets for the two tubes that attach to the framerails are positioned just behind the oval-shaped "access holes" on each side of the rear unibody. Before welding the brackets in place, Crazy Don secures the 3/4-inch Heim joints for the side tubes, and then adds a few degrees of downward angle to each bracket to ensure the rear retains its full motion (up/down) and doesn't bind when the 'Stang launches.
UPR developed a chrome-moly locator for Fox-through-New Edge Mustangs (PN 2013; $299.99), and the part apparently is just what Rich Bach's '90 'Stang needed to cure it of top-end uncertainty when Rich is clicking off mid-8s on 275/60-15 drag radials. Rich had Don Helsel of Crazy Don's Chassis Works in Island Park, New York, handle installation duties-leveling the brace is a critical part of the install.
If you're a welder, installing this piece can be a DIY effort. However, if you're not confident with a MIG or TIG machine, we strongly recommend you seek the assistance of a chassis expert. That's what Rich did, and we recorded the event for you in the accompanying photos.
 As a safety precaution, Crazy...  As a safety precaution, Crazy Don made up this neat wishbone safety-loop, which is designed to catch the tail section of the locator in the event that the 5/8-inch fastener falls out and the tail drops from the mount at high speed. |  "With the wishbone installed,...  "With the wishbone installed, I made some test passes at the track. I noticed right away that my Mustang's rear suspension has stiffened up considerably, and the only rocking that the car did was generated by the tires' movement, not the rearend's," said Rich. "Thanks to Jeremy's (UPR Products) suggestion that I try the wishbone, I'm now able to drive my car through the quarter with ease, instead of hanging on and hoping that the back end is going to stay behind me." |  Crazy Don welds the mounting...  Crazy Don welds the mounting tabs for the locator's Teflon-lined, 5/8-inch rear Heim joint, directly below the center of the rearend housing. The Heim joint is adjustable (in or out), and is the union point for the tubes that are connected to the Mustang's framerails. |