We offer custom-built “bolt in” units, with your choice of gear ratios, aluminum or iron cases, Detroit Lockers, various posi units and spools for 28 or 31 spline axles, single or double ribbed nodular iron case, aluminum or iron pinion supports and companion flanges. Listed are several complete assemblies with gears, all of which can be upgraded with the NASCAR pinion bearing, safety wired ring gear bolts and lightened and/or REM treated gears. NOTE: True-Tracs require specific axle lengths, so please call and speak to a Cobra representative for assistance.