SKU: STGN1980
UPC: 679460120346
MPN: N1980
The Strange Ford 9in S-Trac Differential is a helical-gear, torque-biasing unit built for full-bodied street and track cars that demand consistent traction without the maintenance of a clutch-style limited-slip. It fits the Ford 9" platform with 35 spline axles and is engineered for cars running the 1/4 mile in low 9 seconds or slower, which also makes it a sound pick for road racing, off-road, and autocross duty. Buyers stepping up from an open carrier or a worn clutch-pack unit get smooth, progressive power transfer and quiet operation. It carries STRANGE part number N1980 and ships ready for installation in a compatible main case.
The S-Trac works mechanically through 12 pinion gears that bias torque between the wheels, so there are no cones, springs, or clutches to wear out over time. Case halves are forged steel and heat treated, while the internal pinion gears are 9310 chrome moly steel that has been both heat treated and cold treated for strength under repeated hard launches. A dry film solid lubricant coating on the thrust surfaces reduces friction where the gears load against the case. Note that the S-Trac requires an aftermarket 3.250" bore case with 35 spline axles cut to a 30 degree pressure angle, and no synthetic gear oil is permitted. STRANGE backs the unit with a lifetime warranty per manufacturer specifications. Pair it with the correct ring and pinion for your gear ratio.
This differential earns its place in high-horsepower street machines, bracket cars, and dual-purpose road race builds where a clutchless, low-maintenance limited-slip keeps both tires working off the line and through corners. Because torque transfer is progressive rather than abrupt, it behaves predictably on the street and stays quiet in daily driving. If you are building or refreshing a 9" rear, browse our complete drivetrain selection for carriers, axles, and supporting hardware, along with the pinion yoke needed to finish the assembly.
This S-Trac fits the Ford 9" platform with 35 spline axles. It requires an aftermarket 3.250" bore case and axles cut to a 30 degree pressure angle. Confirm your case and axle specifications match before ordering to ensure correct fitment.
No. The S-Trac is a helical, torque-biasing differential that works entirely through gear interaction. There are no cones, springs, or clutches to wear out, which is why it runs quiet and needs less maintenance than clutch-style limited-slip units over its service life.
No. Per manufacturer specifications, synthetic gear oil is not permitted in the S-Trac. The thrust surfaces use a dry film solid lubricant coating, and running synthetic fluid can interfere with the way the differential is designed to operate.
Yes. The torque-biasing design transfers power progressively rather than abruptly, so it behaves predictably on the street and stays quiet in daily use. It is recommended for full-bodied street and track cars running the 1/4 mile in low 9 seconds or slower.
STRANGE backs the S-Trac with a lifetime warranty per manufacturer specifications. The forged steel case halves and heat-treated 9310 chrome moly internal gears are built to hold up under repeated hard launches and demanding track use.
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