design required new sealing and lubrication strategies, Ford did extensive laboratory and road testing of the new axle seals to ensure that they were satisfactory. Road testing in sand, dirt, and gravel took place in northwestern Arizona surrounding the Arizona Ford Proving Grounds in Yucca. As a result of this testing, some seals and bearings were modified before production began.
The Dana 30 proved to be a good first volley across the bow of competitors in terms of upgraded axles. It gave up just a bit of ground clearance (1 to 1.5 inches) to go along with the slightly increased housing size. Ford did consider using the high-pinion Dana 44 that was introduced in the 1966 Ford F-100, but driveshaft clearance problems precluded its adaptation. Front brakes were of the drum variety and measured 11x2 inches.
The testers’ impressions of the brakes were one area that showed how much perceptions and expectations of vehicle performance have changed since 1966. Nearly every test of the first Bronco praised the “large” brakes and their holding power, with some going so far as to exclaim that power brakes were not necessary because the existing setup was so strong and required such low pedal pressure. Those were the expectations in the mid-1960s. In just a few years, with power disc brakes much more prevalent on passenger cars, reviewers complained of fading, pulling, and excessively high pedal effort.
Rear Axle
The Bronco rear axle was Ford’s familiar 9-inch (named for the diameter of its ring gear), the first variant of which had been introduced in Ford’s 1957 cars. By the time of the Bronco’s introduction, the 9-inch rear axle had gained a reputation for strength and ease of gear changes due to its drop-out differential assembly. In the Bronco, it was offered with two capacities: 2,780 pounds and 3,300 pounds, now known as the “small bearing” and “big bearing” rear ends, respectively. Each offered the option of a clutch-type limited-slip (Traction-Lok in Ford-speak) and axle ratios of 4.11 and 4.57:1 behind the 6-cylinder engine. When the V-8 was introduced, Ford added a 3.50:1 ratio to the mix. The 1966 rear axle housing is unique and identifiable from other years of the first generation by an inspection/fill plug on the rear of the housing.
Although the 9-inch rear axle was appreciated for its strength, it did suffer in the ground clearance department compared to the axles offered in the CJ-5 and Scout, hanging 1.5 to 2 inches lower than the competition. The rear brakes on all rear axles had a 10-inch diameter and measured 2.5 inches wide.
The Bronco’s header front suspension was one of its strongest selling points when it was introduced and continued to be a prime reason for its success; none of its primary competitors switched to coil springs during the Bronco’s lifetime. At its introduction, Ford touted its superior ride characteristics, improved handling, and ability to allow tighter turning circles as its key attributes.
Coil springs generally ride better than their leaf-spring counterparts due to the lack of internal friction inherent in leaf springs. Because the leaf springs on the front of solid-axle vehicles must serve a locating function in addition to providing ride comfort, they end up being stiffer because they are mounted farther inboard from the wheels than coils to achieve an acceptable turning radius.
Ford’s radius arm suspension also had excellent anti-dive characteristics, with Ford Bronco engineer Paul Axelrad noting that the Bronco showed 102 percent anti-dive when 70 percent of the braking was accomplished at the front wheels. That is important during panic stops and when performing snowplowing chores with a heavy plow on front.
Body
The Bronco featured body-on-frame construction, combining a ladder frame with a unitized body (the cargo section of the body and the front seat and engine area were all one piece rather than separate structures as on conventional pickup trucks). The Bronco’s frame was fully boxed along the length of its two rails and its two primary crossmembers, which made it extremely strong and stiff. The combination of the Bronco’s unitized body and strong frame made it about three to four times torsionally stiffer than a pickup truck of the same era. Adding a roof increased the torsion and bending stiffness and adding doors increased the bending stiffness. The front and rear bumpers also provided a substantial contribution to the torsional stiffness.
This test involved test dummies in the front and rear seats, with dummy number-9 eerily looking at the camera as the front of the truck collapses around its legs. The rear-seat dummy has an arm outstretched, likely mimicking the reaction of a passenger in such a collision. (Photo Courtesy Jeff Trapp)
This Bronco intentionally being destroyed is a cringe-worthy moment for enthusiasts today. An instrumented “crash test dummy” is leaning forward in the rear seat. The front buckets are leaning forward and based on the location of the body relative to the axles, it appears the body has shifted forward on the frame. (Photo Courtesy Jeff Trapp)
Caught in mid-roll by the camera, window glass flys across the grass ahead of the rolling truck. A complete drivetrain is visible on this test vehicle, suggesting that a complete vehicle was used for the test. Based on the trees in the background and the terrain, all of these test photos appear to have been taken at the Dearborn Proving Grounds. (Photo Courtesy Jeff Trapp)
SUSPENSION DEVELOPMENT
The development of the monobeam front suspension is a fascinating story. The initial design of the suspension was done in parallel with the development of the famed Twin I-Beam 2WD front suspension, which was introduced on 1965 Ford pickups. In the early 1960s, a feasibility vehicle was built to design and test the monobeam front suspension. Based on a 4WD pickup, it featured a 5-foot cargo bed and rode on a 106-inch wheelbase.
The truck was built in several configurations with both 6- and 8-cylinder engines and 3- and 4-speed transmissions in front of a single-speed transfer case. The evaluation of this vehicle confirmed the desired handling, maneuverability, and performance of the monobeam front axle concept.
The feasibility vehicle’s radius arms for the suspension were stamped pieces taken from a Twin I-Beam suspension and modified at the ends to attach to the monobeam axle housing. These radius arms attached to the axle housing with large rubber bushings, which worked fine in testing but were deemed to be unnecessarily complex for production. The final design used forged radius arms that clamped wedges on the axle housing with rubber isolators between the arms and the axles. Ford tested this configuration for 500,000 cycles without failure and deemed it acceptable for production.
A vehicle that uses a leading arm suspension like the monobeam front end with radius arms requires some type of lateral control for the axle as well. Ford chose to use a panhard rod, or track bar in Ford lingo, to locate the front axle. Because the location of the track bar is critical from a vehicle handling standpoint, Ford tested several mounting locations for the bar mounting points and tested them on ride and handling courses to arrive at the ideal configuration. After the mounting points were set, a complete track bar system was fatigue-tested in the laboratory by subjecting it to simulated vehicle loads for more than 1,000,000 cycles without failure.
It’s a little-known fact that the first Bronco package study included mirror-image front and rear suspensions. A similar configuration was later used by other manufacturers, but in the early 1960s, Ford decided against coil springs in the rear due to the encroachment into that ever-important ramp break-over area by the radius arms and their mounting brackets.
Instead, Ford used a traditional Hotchkis-type suspension with leaf springs anchoring each rear corner. With the standard 3,900-pound gross vehicle weight (GVW) package, the leaf springs had five leafs and the optional 4,700 GVW package springs had six in their packs. Rear shocks were mounted angling forward from the axle to the frame