The Eaton Detroit Truetrac is a helical gear-driven limited-slip differential that maximizes available traction while sharpening handling and drivability. It works smoothly and automatically, needs no maintenance, and avoids the on/off behavior of a locker, which makes it a strong choice for street, tow, and trail use.
- Type: Helical gear limited-slip differential
- Axle: Ford 9in
- Ring gear: 9in
- Axle shaft diameter: 1.20in
- Spline count: 28
- Gear ratio: 3.25 and up
- Part number: 912A587
Axle Fitment
Fits the Ford 9in axle, 28-spline, 1.20in axle shaft diameter, with 3.25 and numerically higher ratios. This axle appears across 1957-1980 Ford applications and many 9in swaps. Confirm your axle and spline count.
FAQ
What axle does the Truetrac 912A587 fit?
It fits the classic Ford 9in axle with a 28-spline count and 1.20in axle shafts, using 3.25 and numerically higher gear ratios.
Will it work in a Ford 9in swap?
It fits the Ford 9in axle by spline count and ratio range. Confirm your carrier bearing size and 28-spline shafts before ordering.
Does the Truetrac need maintenance?
No. It is a helical limited-slip that operates automatically and smoothly with no maintenance and no locker on/off behavior.

