How do I identify my rear axle type?

Per the document, take three measurements on the rear end assembly: 1) outside bearing diameter, 2) housing flange dimensions, and 3) stud pattern and bolt circle on the axle flange, then compare them to the diagrams. Rely on measurements, not appearance.

What are the housing end dimensions for a Small Ford rear axle?

The Small Ford diagram shows a 2.835 diameter bearing bore, 2.000 vertical spacing, and 3.375 horizontal bolt spacing.

How do I tell a Big Ford from a Big Ford (New Style) housing end?

Both show a 3.150 diameter, but the Big Ford has 2.375 vertical spacing and 3.500 width, while the Big Ford (New Style) has 2.000 vertical spacing and 3.562 width.

What are the 8.8" Ford housing end dimensions?

The 8.8" Ford diagram shows 3.410 width, 2.840 diameter, 1.680 vertical spacing, and 3.076 across the bottom.

Can custom rear ends differ from these diagrams?

Yes. The document notes that custom rear ends may use axle bearings and housing flange patterns different from original equipment, so measure carefully.

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Rear Axle Identification Chart - Ford, Chevy, Mopar Housing Flange Dimensions

Rear-axle identification chart with dimensioned housing-flange drawings

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Reference chart for identifying rear axles by housing-flange dimensions and bolt patterns across makes.

AI caption November 2014 · Photo 391 of 393

This one-page reference chart, titled 'Identify Your Rear Axle,' helps readers identify the type of rear axle (rear end) on their vehicle using three key measurements: outside bearing diameter, housing flange dimensions, and the stud pattern/bolt circle on the axle flange. It cautions that custom rear ends may use bearings and housing flange patterns different from original equipment, and stresses relying on measurements rather than appearance since rear ends may differ visually from the diagrams. Ten labeled housing-end flange diagrams are shown with dimensions in inches: Small Ford (2.835 dia bearing, 3.375 bolt spacing), Big Ford (3.150 dia, 3.500), Big Ford New Style (3.150 dia, 3.562), 8.8" Ford (2.840 dia, 3.410 x 1.680, 3.076), Chevy Special (3.150 dia, 3.125 x 2.437, 2.687), 8-3/4 and 9-3/4 Mopar / Dana 60 (2.875 dia, 3.188 x 1.594, 3.562), Olds/Pontiac (3.150 dia, 2.875), 8-1/4 and 9-1/4 Mopar (2.530 dia, 3.182 x 1.568, 3.568), Mark Williams (3.150 dia, 3.000 square pattern), and 12 Bolt Chevy (3.125 x 2.437, 2.687). An axle flange cross-section diagram illustrates how offset is measured. Useful for anyone ordering axles or identifying a swapped rear end.

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Frequently asked questions

How do I identify my rear axle type?: Per the document, take three measurements on the rear end assembly: 1) outside bearing diameter, 2) housing flange dimensions, and 3) stud pattern and bolt circle on the axle flange, then compare them to the diagrams. Rely on measurements, not appearance.
What are the housing end dimensions for a Small Ford rear axle?: The Small Ford diagram shows a 2.835 diameter bearing bore, 2.000 vertical spacing, and 3.375 horizontal bolt spacing.
How do I tell a Big Ford from a Big Ford (New Style) housing end?: Both show a 3.150 diameter, but the Big Ford has 2.375 vertical spacing and 3.500 width, while the Big Ford (New Style) has 2.000 vertical spacing and 3.562 width.
What are the 8.8" Ford housing end dimensions?: The 8.8" Ford diagram shows 3.410 width, 2.840 diameter, 1.680 vertical spacing, and 3.076 across the bottom.
Can custom rear ends differ from these diagrams?: Yes. The document notes that custom rear ends may use axle bearings and housing flange patterns different from original equipment, so measure carefully.