Ford Bronco
1966–77 early

Factory gearing, tires, angles and brakes for the Bronco, and what the usual upgrades do to it. Every number is from the maker's own figures unless the calculators say otherwise. A few figures here are still waiting on a factory document; the calculators mark them.

Use this truck in the calculators

92 in wheelbase · 26.9 in front · 33.2 in rear overhang

Axle ratio3.5–4.57Factory, by trim

Crawl ratio38.3:1Best trim: 1966-70 std 7.35-15 (170/200 Six or 289/302 V8, 3-speed) (7.35-15 4PR tubeless tires)

Angles40.6 · 29.1 · 27.2°Approach, breakover, departure

Clearance8.22 in6.4 to 8.22 in by trim

Highway mpg14Estimate, not EPA rated

Trims

7 we have figures for

Trim	Tire	Transmission	Axle	Angles	Clearance	Open
1966-70 std 7.35-15 (170/200 Six or 289/302 V8, 3-speed) (7.35-15 4PR tubeless tires)	26.5	3-speed manual, column shift, 3-speed manual, column shift	3.5 / 4.11 / 4.57	40.6 · 29.1 · 27.2	6.6 in	Use →
1966-71 optional 6.50-16 tube-type (needs free-running hubs + limited slip) (6.50-16 6PR TT tires)	28.8	3-speed manual, column shift, 3-speed manual, column shift	3.5 / 4.11 / 4.57	45 · 34 · 31.2	8.2 in	Use →
1971-72 std E78-15 (E78-15 4PR tires)	26.5	3-speed manual, column shift, 3-speed manual, column shift	3.5 / 4.11 / 4.57	40.2 · 28.59 · 26.88	6.4 in	Use →
1973-75 std E78-15 (200 Six 4.11 / 302 V8 3.50; C4 auto with V8) (E78-15B tires)	26.5	3-speed manual, column shift, 3-speed manual, column shift, 3-speed automatic	3.5 / 4.11 / 4.57	40.2 · 28.6 · 26.9	6.4 in	Use →
1973-77 optional 7.00-15 tube-type (7.00-15 C/D TT tires)	28.3	3-speed manual, column shift, 3-speed automatic	3.5 / 4.11	44.1 · 33 · 30.1	8.1 in	Use →
1976-77 std E78-15 (302 V8, 3.50) (E78-15B tires)	26.5	3-speed manual, column shift, 3-speed automatic	3.5	39.3 · 25.9 · 29.6	6.4 in	Use →
1977 4900 lb GVWR package G78-15 (G78-15B tires)	27.7	3-speed manual, column shift, 3-speed automatic	3.5	40.3 · 28.6 · 26.6	6.4 in	Use →

Size

Wheelbase: 92 in
Front overhang: 26.9 in
Rear overhang: 33.2 in
Height: 69 in
Body: Short wheelbase SUV
Stock tires: 26.5, 27.7, 28.3, 28.8

Transmissions and low range

3-speed manual, column shift (Ford RAT, six-cylinder): 3.41 · 1.86 · 1
3-speed manual, column shift (Ford RAN, V8): 2.99 · 1.75 · 1
3-speed automatic (C4), 1973-77 V8 only: 2.46 · 1.46 · 1
Low range, d20early: 2.46:1
Low range, d20late: 2.34:1

Axles

Front: Dana 30 closed-knuckle (1966 to mid-1971, 2500 lb), Dana 44 (mid-1971 to 1977, 3000 lb)
Rear: Ford 9 in (2780 lb std, 3300 lb HD); some very early 1966 trucks reportedly Dana 44
3.5 ratio: 1966-70 std 7.35-15 (170/200 Six or 289/302 V8, 3-speed) (7.35-15 4PR tubeless tires), 1966-71 optional 6.50-16 tube-type (needs free-running hubs + limited slip) (6.50-16 6PR TT tires), 1971-72 std E78-15 (E78-15 4PR tires), 1973-75 std E78-15 (200 Six 4.11 / 302 V8 3.50; C4 auto with V8) (E78-15B tires), 1973-77 optional 7.00-15 tube-type (7.00-15 C/D TT tires), 1976-77 std E78-15 (302 V8, 3.50) (E78-15B tires), 1977 4900 lb GVWR package G78-15 (G78-15B tires)
4.11 ratio: 1966-70 std 7.35-15 (170/200 Six or 289/302 V8, 3-speed) (7.35-15 4PR tubeless tires), 1966-71 optional 6.50-16 tube-type (needs free-running hubs + limited slip) (6.50-16 6PR TT tires), 1971-72 std E78-15 (E78-15 4PR tires), 1973-75 std E78-15 (200 Six 4.11 / 302 V8 3.50; C4 auto with V8) (E78-15B tires), 1973-77 optional 7.00-15 tube-type (7.00-15 C/D TT tires)
4.57 ratio: 1966-70 std 7.35-15 (170/200 Six or 289/302 V8, 3-speed) (7.35-15 4PR tubeless tires), 1966-71 optional 6.50-16 tube-type (needs free-running hubs + limited slip) (6.50-16 6PR TT tires), 1971-72 std E78-15 (E78-15 4PR tires), 1973-75 std E78-15 (200 Six 4.11 / 302 V8 3.50; C4 auto with V8) (E78-15B tires)
Ratios made for it: 4.11 · 4.56 · 4.88 · 5.13 · 5.43

Brakes

Front: Drum
Rear drum: 11.00 in, 279 mm
Rear: drum

Suspension

Front: radius arms with track bar, coil springs
Rear: leaf springs, solid axle
Rear layout: Leaf springs

Fuel economy

Highway, not EPA rated: about 14 mpg
Where it comes from: Road test, overall average (1966 Bronco 170 six, 3-speed)
Source: curbsideclassic.com

Brake upgrades

What bigger tires need →

Wilwood Dynapro 6R front disc kit 140-13303N (66-75 Bronco)11.8 in rotor · 6-piston · 15 in wheels or bigger · $1,429CJ Pony Parts DBF227-V listing price; Wild Horses lists the same kit (140-13303N) without a price shown.

Aftermarket bumpers

9 listed

Makers almost never publish angles, bottom heights or how far a bumper tucks, so these fill in as owners measure them. Measured yours? Add it on the rig page and every owner of this Bronco sees how it does on their tires and lift.

Front 5

Rear 4

Every calculator, set up for the Bronco

Tire sizeBigger tires: speedo, clearance, angles and brakes.Compare tires RegearHighway RPM on every ratio and mpg.Pick your gears Crawl ratioHow slow it creeps, against other trucks.Work out crawl SpeedometerWhat it really reads on new tires.Fix your speedo LinksAnti-squat and what a lift does to it.Check your links Your rigBuild sheet and measured angles.Start a build sheet LeaderboardsWhere the Bronco ranks against every stock truck.See where it ranks

Source: archive.org. Front and rear ratios were not identical from the factory (front 4.10 with rear 4.11, front 3.54 with rear 3.50), so order a matched pair when regearing; Dana 30 fronts have far fewer ratio choices than the Dana 44.

Use at your own risk. These calculators are here to help you plan and to inform your decisions, not to sign off on a build. Many numbers are estimates worked out from factory figures, and some factory figures are not yet confirmed. Check every number against your own truck, its manuals and a qualified shop before you buy parts, cut, weld, lift, regear or drive on it. Long Range Desert Tools is not liable for anything you do based on these calculators or their results. The full terms are in our policies.

Ford Bronco1966–77 early