It's built strong, lasts long, and hooks the tires so hard it's just plain wrong. This is a fair description of Detroit Locker's new Detroit Truetrac locking differential. Whether it's an 8.5-inch ring gear 10-bolt rearend, or a heavy-duty 8.875-inch 12-bolt bad boy, the Truetrac differential is capable of lowering acceleration times without excessive wear to internal components or the rear tires. We wanted to see what makes the Truetrac design tick, and the guys at Currie Enterprises offered to take us through a 12-bolt buildup and the benefits of a Detroit Truetrac locking differential.
Today's world of aftermarket bliss offers so many types of differentials it's difficult to determine which is best for your needs. Straight-line acceleration lends itself to a spool type for absolute positive axle power, while high-performance street/strip lockers fall within an overwhelming sea of choices. The key to a street-style locking differential is how to compensate for varied wheel speed around corners, while also being able to deliver constant and equal drive force to each drive axle when straight-line acceleration is needed. Addressing these issues are some of the most popular locking-differential designs featuring spring tension-induced cones, friction plates, air pressure, and electrically operated setups. Each of these works well for a specific application, but also requires some sort of maintenance or additional support system. With the use of a Truetrac differential design, Detroit Locker has been able to provide a wear-free, gear-driven, limited-slip unit.
The Detroit Truetrac limited-slip differential features a patented design of parallel-axis planetary-helical gears that split torque with such ease there is little driveline disturbance from open-differential action to engaged-axle drive. The helical gears require no air tanks to mount, wires to cross, or friction components to replace. It provides a wear-free environment that is capable of handling strong doses of torque from heavy-hitter street/strip engines. By eliminating conventional clamping-friction components inside the differential, the helical gear design is capable of handling much more torque capacity. When combining the affordability of a Truetrac differential design with characteristics of wear-free maintenance and loads of additional torque-carrying capacity, it's easy to see why a helical gear-driven posi is so popular.
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Our starting point was the famous 12-bolt rearend. General Motors produced Chevrolet 12-bo
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Currie cut off the housing ends of our '69 Chevelle axle and replaced them with 9-inch sty
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Truetrac differentials use parallel-axis planetary-helical gears to split torque, and can
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Our converted 9-inch housing ends require the axles to be equipped with a lock collar, bea
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Our Currie technician fastened the ring gear to the Detroit Truetrac with 50 lb-ft of clam
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With the pinion gear standing on the press, the pinion bearing was pressed into position.
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The differential with carrier bearing installed must be carefully set in place using speci
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Once the pinion shim was installed and the bearing was pressed over the shaft, the entire
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From the pinion head back, a depth shim and bearing fit over the 30-spline shaft and ride
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The standard car yoke size is a 1310-series that measures 3 1/2 by 1 1/16 inches. The next
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With all shims in place and our differential fastened securely, we checked the backlash of
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To keep the lube inside our 12-bolt, Currie installed a pinion seal by gently tapping it i