12-Bolt Vs. 9-Inch
"A 9-inch rearend is a poor choice for cars that utilize torque arms, such as the late-model F-body, mostly due to the substantial increase in road and driveline noise through the torque arm itself," says Jeff. "Also, the 9-inch does not adapt well to ABS systems. This is why we don't make a 9-inch rearend for late-model F-bodies. For these cars, the 12-bolt is a significant upgrade over the factory 7.625-inch rearend. For earlier F-bodies and other non-torque-arm GM vehicles, the 9-inch provides an excellent foundation. The only notable con for the 9-inch is that axles with 35 or more splines require a Detroit Locker or a spool, which some people do not like to use. Lockers also make for a pricier rearend. Likewise, the driveshaft has to be narrowed or replaced when using a 9-inch, as opposed to a 12-bolt that allows retaining your stock driveshaft. However, if your application requires a replacement rearend, then it certainly requires an upgraded driveshaft."
Perhaps due to its extensive use in high-end drag car chassis, chrome-moly has a certain mystique in automotive applications. However, coughing up extra dough for a chrome-moly rearend housing probably isn't necessary for most applications. "Steel axlehousings and tubes are made from either mild steel or chrome-moly, but the vast majority are made from mild steel," says Jeff. "Housings made of mild steel provide adequate strength for most drag racing applications, and every street and drag racing steel housing we manufacture is made from mild steel. Most of the housing's strength is derived from its tube size, back brace, basic housing design, and how it is welded together. The aforementioned points are far more important than the difference between chrome-moly and mild steel."
Whether it's due to unclear rulebooks or hard-headed racers, there seems to be a fair amount of confusion when it comes to selecting the right wheelstuds. Ideally, use the shortest wheelstuds possible. Shorter studs are lighter, allow easier wheel removal, and do not experience the same leveraging loads as longer studs. "There are two common aftermarket stud sizes, 1/2x20 and 5/8x18," says Jeff. "We offer 2- and 3-inch-long 1/2-inch-diameter studs for street or mild drag use, but do not recommend a 1/2-inch stud longer than 3 inches for safety concerns. For dedicated drag racing vehicles, 5/8-inch studs are highly recommended. Since 5/8-inch studs, unlike 1/2-inch studs, do not use conventional lugs, it is important to make sure that wheel thickness, rotor hat thickness, and any wheel spacers being used are compatible with 5/8-inch studs."
"Forgings are mostly used to reduce machining time and scrap metal," explains Jeff. "However, a forging also provides excellent grain flow of materials, which is superior to billet components. When we first started making axles in the late '60s, we used two pieces. One piece of 7-inch-diameter steel for the flange and one piece of 2-inch-diameter steel were welded together before machining the shaft. Today, we manufacture our axles from premium-grade forgings, then have dedicated CNC lathes for rough-turning and finish-turning the axles. Up until the late '90s, we fully ground the bearing surface and axle flange, but with today's tools and machinery, we are able to hold exacting tolerances and provide an excellent finish with our dedicated CNC lathe. Less than 10 years ago, we used manual multispindle drill presses to drill and tap the bolt-circle pattern and manual hobs to hob the axle splines. Today, we have dedicated CNC vertical mills and a CNC hob, which are far faster and more accurate. That means lower prices and better quality for our customers."
To make sure your axles stay put, C-clip eliminators are something every street/'strip vehicle should have. "Most sanctioning bodies, such as the NHRA and IHRA, have rules that specify an e.t. or trap speed at which the use of a C-clip eliminator kit is mandatory," explains Jeff. "However, I would recommend a C-clip eliminators kit for any application that has been enhanced beyond its factory performance. Remember, if the axle or the side gear fails with C-clips, the entire axle will slide out of the rearend."