Early Bronco Ford 9-inch Rear Axle Housing

Early Bronco Axle Housing Identification.

All 66-77 Ford Broncos came with a Ford 9-inch rear end. However, there were four different axle housings offered throughout the early Bronco's 12 model-year run.

• 66-75 Ford Bronco Small Bearing Axle
  • Backing Plate ID Numbers: FF55264, FF55265
  • Brake Drum: 10" x 2.5"
    
    
• 66-75 Ford Bronco Large Bearing Axle with 11" Brake Drums
  • Backing Plate ID Numbers: 319130L, 317363L, 319130R, 317364R
  • Brake Drum: 11" x 1.75"
    
    
• 74-75 Ford Bronco Large Bearing Axle with 10" Brake Drums
  • Backing Plate ID Numbers: 80174L, 80175R
  • Brake Drum: 10" x 2.5"

• 76-77 Ford Bronco Large Bearing Axle with 11" Brake Drums
  • Backing Plate ID Numbers: 3203097L, 3203098R
  • Brake Drum: 11" x 2.25"

The backing plate numbers listed above are a great way to identify your specific axle housing. However, these numbers can be extremely difficult to read through the decades of grime that builds up. To more easily distinguish between large and small bearing rear axles you can inspect the ends of the axle housing. A small bearing axle shows no significant increase in size at the axle bearing pocket near the backing plate, whereas a large bearing axle displays a noticeable size increase at this junction.

Each configuration includes a driver and a passenger side axle, with corresponding backing plates and brake drums specific to each set. It is important to note that these components are not universally interchangeable. However, the 1966-1975 small bearing and the 1974-1975 medium duty large bearing can use the same brake drum.

You can also identify which axle housing you have by measuring the inside of the Bronco rear brake drum. The ID of the brake drum will be either approximately 10" or 11". If you have 10" brakes, measure the axle bearing diameter. It should either be 2-7/8" (small bearing) or 3-1/8" (large bearing). Of the two 11" brake drum options, the 66-75 Ford Bronco rear axle version features a narrower drum and brake shoes, marked as 11 x 1-3/4". This is compared to the 76-77 Bronco version which uses an 11 x 2-1/4" drum and shoe.