why the 1966 Shelby GT350 went from 15- to 14-inch-diameter rims? It wasn’t a move to decrease vehicle height or drop the center of gravity in search of even better handling, although it did those things. Rather, after specifying 7.75-15 Goodyear Blue Dot race tires in 1965, Shelby and his workers found they had to spend a lot of time trimming the stock Mustang wheel lips to clear the larger diameter tires. By switching to 14-inch Goodyears for 1966, more than an hour of handwork per car was saved and the tire-rub problem was cured.
78 Pre-production GT350 track testing revealed the stock upper shock absorber mounts (a.k.a. “beehives”) were too thin and needed fortification to maximize the effectiveness of the Koni shock absorbers at the front of the car. The simple remedy was the addition of two 3/4-inch flat washers atop each beehive to distribute localized stress better. Each washer was tack welded in position to prevent loss during assembly and service. Interestingly, these reinforced mounts were installed at the San Jose Mustang plant rather than at Shelby’s 6501 Imperial Highway conversion facility.
79 The Mustang’s Falcon economy car roots are closer to the surface on 6-cylinder models than on V-8 cars. While V-8–powered ’Stangs were factory equipped with 10-inch drum brakes and five-lug hubs/wheels, base models with the 170- or 200-ci 6 rolled on the Falcon’s four-lug hubs and wheels. Early 1965 V-8 Mustangs came standard with 13-inch rims. These five-lug, 13 × 4½–inch-diameter hoops are very rare today because 14-inch rims and tires were optional for as little as $15.67 (black sidewall, nylon).
80 Mustang spotters in the 1964–1966 time frame knew to give extra respect to anything rolling on redline tires. That’s because Ford specified beefy 6.95×14 Firestone dual red-band tires any time the 271-hp Hi-Po 289 was ordered. Buyers who wanted a little more anonymity could revert to same-size whitewalls or blackwalls at no extra charge. I’ll take the redlines!
81 The 15-inch rims were typically found on full-size Ford models such as the Galaxie and LTD, but early in the Mustang production run, it was possible to order 5.70 or 5.90×15 tires and rims as part of the handling package on V-8 cars. Because of tight clearance, they were canceled in September 1964. After that, the next (non-Shelby) 15-inch Mustang wheel offering didn’t become available until 1969.
82 Part of the 1965 GT350’s reputation as a brutal, no-compromise beast stems from the replacement of the K-code Mustang’s Traction-Lok 9-inch rear axle with a ratcheting differential sourced from Detroit Automotive. The so-called Detroit Locker replaced the Traction-Lok’s conventional spring-loaded friction clutches (also available in the smaller 8-inch Hotchkiss-style rear axle) with a ratcheting differential. Free from clutch slippage, the locking differential delivered full power, equally, to both rear tires. The downside was its on/off nature and aggressive engagement characteristics. When cornering, the unit tended to (either) emit loud clicking sounds as the ratcheting gears rode past each other, or turn the inside tire at the same speed as the outside tire with the attendant chirping sound of tires squealing in protest. But in a straight line, the added stability of equal tire thrust was its virtue. Shelby made the Detroit Locker an extra-cost option for 1966.
This original 1965 GT350 Detroit Locker displays the “dog gear” ratchet assembly that made it lurch, and work so well. See Fact No. 82 to learn why Ol’ Shel made it an option for 1966 and beyond.
83 Carroll Shelby went to extreme measures in 1965 to cure Mustang’s penchant for violent axle hop on full-throttle acceleration. A pair of tubular-steel traction bars was welded to brackets atop the outboard ends of the rear axle housing. The rear floor was cut open and the bars entered the car; the bars were then bolted to beefy steel mounts welded to the floorpan. Because they are located above the axle and leaf springs, this arrangement has come to be known as the “overrider” traction bar. Thanks to the GT350’s no-back-seat mandate (the SCCA didn’t accept the Mustang with its standard back seat as a sports car), conflict with rear-seat passenger’s feet was a non-issue. What was an issue were the many man-hours required to fabricate and install these complex traction bars (see Fact No. 7 for more).
84 Although all 561 of the 1965 GT350s received the time-consuming overrider traction bar conversion, Shelby reconsidered his traction bar strategy for 1966. Instead, more conventional under-rider–style traction bars were sourced from the Traction Master Company of nearby Burbank, California. A pioneer in bolt-on traction aids since the mid-1950s, Traction Master bars were also factory installed on the Sunbeam Tiger and certain high-performance Studebakers. Mounted entirely under the chassis, the only welding involved a single mounting bracket (per side). Even though the first 252 1966 GT350s retained the elaborate overrider bars, the Traction Master bars were phased in as a running change and the vast majority of the 1966 GT350s (2,378 built) used them.
85 Getting back to the complexity of the 1965 overrider traction bar program: The necessary pass-through slots cut into the Mustang’s rear floorpan had to be patched with a flexible cover in order to meet Ford Minimum Standards Regulations for road noise and cabin sealing while also allowing 6 inches of up-down suspension travel. No fewer than three strategies were employed. The first involved simple flat sheets of rubber; the second called for specially formed fiberglass boxes (the most time-consuming and costly); and the third, a pair of molded rectangular rubber boots sourced from a Ford heavy-truck application. Because of their tall, rectangular form, the truck-sourced boots gave the steel tubes the look of much larger Fairlane Thunderbolt traction bars when viewed from inside the car. The switch to Traction Masters in 1966 was well timed with the SCCA’s easement of its prior (back seat) restriction. The 1965 overrider bars interfered with the bottom cushion.
86 As evidence of Shelby’s new-found (1966) focus on manufacturing efficiency and simplification, the cast-iron bracket locating the axle end of the Traction Master tube to the shock absorber/spring plate and U-bolts was cast with three ears instead of four. This allowed installation of the traction bar without dropping the leaf spring plate and, subsequently, the rear axle, thus saving time. Uneducated Shelby swap meet shoppers often assume the missing ear signifies a broken part. In succeeding years, the Shelby Mustang’s add-on traction aids were simplified further as Ford evolved Mustang’s rear suspension for better axle control at the factory level. I explore this in the next chapter.
87 Even though the 1984 Mustang SVO hosted the showroom debut of four-wheel disc brakes, Ford is known to have experimented with the superior stoppers on first-generation Mustangs. The only disc-equipped survivor from the 1960s is the 1968 Shelby “Green Hornet.” Unique because of its hardtop body style, the 428 test car (born an S-code 390) also served as a development mule for throttle body-style electronic fuel injection and independent rear suspension. Overseen by Shelby American chief engineer Fred Goodell, each of its innovations saw production, albeit years later (EFI in 1983, IRS in 1999). The Green Hornet has been fully restored and occasionally appears at major Mustang shows.
What sets early 1965 brake master cylinders apart from late 1965 units? Fact No. 88 reveals all.
88 Early 1965 Mustangs were fitted with a very unique brake master cylinder with the brake light trigger switch and wiring built into its body. Surprisingly, buyers who wanted power assist (a $58 upgrade) were restricted to drum brakes. The first power-boosted Mustang front disc brakes didn’t arrive until 1967.
89 The lone exception to the manual disc-only rule came from Shelby. Standard GT350s were built with manual front disc brakes (upgraded with metallic pads). When Shelby won a lucrative contract for 1,000 Hertz GT350-H rental cars (1,001 were actually built), Ford hadn’t finalized its power-boosted disc brake testing (to be released for 1967). Shelby was on his own to find the needed brake booster and install it. The solution came from a compact two-stage
