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Step 1:
Choose Rearend

Tip: This calculator works only for cars built for "right-hand traffic."

Tip #2: If you have a Dana or any custom width rearend and want to run original Mopar adjustable tapered ("Set 7") wheel bearings, please email.

Step 2:
Choose Pinion Offset

Tip: Select "Use existing housing or axles" to skip pinion offset and build a rearend around your existing parts.

Tip #2: A pinion offset of "0" places the pinion in the exact center of the vehicle. A positive offset moves the pinion toward the passenger side. A negative offset moves the pinion toward the driver side.

Step 3:
Choose Measurements

Change Brake Gap?

Tip: For "A", "B", "C","D" and "brake gap" measurements, use the schematic above as a reference. Enter all values as inches in decimal form.

Tip #2: A Dana is measured from the BACK, placing the passenger tube on the right of drawing. The others are measured from the FRONT (brake line clip on the back toward top), so the passenger tube is on the left.

Tip #3: DoctorDiff axles have 2.525" (Dana & 8 3/4") and 2.5" (Ford 9") brake gaps. Check the box above to enter a custom value.

Tip #4: You must know/measure your existing brake gap if reusing axles! There are no "standard" values for Ford 9" axles, so make no assumptions.

Step 4: Enter Measurements
(if any)


Passenger Side (A)

Side (B)
Housing Width (C)


Axle Flange to Axle Flange (D)
Nearest 1/16"

Step 5: Click "Calculate"

Stock Length Mopar Axles
Custom Length Mopar Axles
Ford 9" Axles (tapered wheel bearings)
Ford 9" Axles (sealed ball wheel bearing)
Complete Strange 60 Rearend


  1. If you use an existing housing, position it rightside up (brakeline clip toward top on 8 3/4" and Ford 9" housings) and verify that the A, B, and C dimensions above match what you have. If they don't match, you have either entered something incorrectly, or your combination will not work with your existing housing.
  2. If reusing axles, you must enter the brake gap to correctly calculate the housing width.
  3. If you are ordering axles and changed the brake gap, you will require custom axles.
  4. Your brakes will not fit if the brake gap is too narrow so please verify first.
  5. DoctorDiff axles are available in most lengths, but custom axles can be made if necessary.
  6. To calculate "Drum to Drum" width, add 2 times the thickness of your brake drum to (D).