Strange Engineering Rearend & Driveline Components Insight - CHP Insider

Stephen Kim Oct 1, 2008 0 Comment(s)
0810chp_05_z Strange_engineering_rearend_and_driveline_components_insight Floater_axles 2/10

Although they're rarely used in street applications, floater axles have mechanics worth examining. A traditional axle is retained by a retainer plate, and the bearing by a locking collar. The axle flange hangs out of the housing 2.335 to 2.835 inches, so it becomes leveraged and stressed at the axle flange as well as at the bearing journal. Tire shake, torque, weight transfer, tire grip, and wheel and tire weight all stress the axle outboard of where the bearing sits. No issue for a Super Comp car, but for a Pro Mod car, this stress can result in axle failure. If an axle fails at the bearing journal, it will separate from the car along with the wheel. "A floater rearend solves this problem by using floater spindles, hubs, a driveplate, and a straight shaft," explains Jeff. "The straight shaft is splined on both ends, and one end slides into the spool while the other engages into the driveplate. This setup cures the leverage issue, and if the axle fails, the wheel is still attached to the floater hub. In a floater, the axle is not relied upon to retain the wheel; its only function is to drive the steel driveplate."

Gear WhineA whiney ring-and-pinion set can make an otherwise pleasant freeway cruiser unbearable to drive, so how do you avoid the noise? "Certain rearends are more prone to noise than others," says Jeff. "For instance, a 7.5-inch 10-bolt is far less forgiving than a 9-inch rearend, partly because of gear size and partly because of the rearend design. Also, some gear ratios are more prone to noise. When a new gearset is installed, it should be set up like a brand-new assembly with new shims, bearings, and ring gear bolts, which will significantly reduce the potential for whine."

Ring-And-PinionAftermarket ring-and-pinion sets, in most cases, are no stronger than OE gearsets. The advantage of aftermarket gearsets is their wider range of gear ratios. In some cases, aftermarket companies use a better material, but the difference is subtle. "The true quality of the gear is evident in how well the gear sets up and how quiet the gearset is in operation," Jeff opines. "Competition gearsets are designed for drag racing only, and are manufactured from 9310 steel, a high-impact material. This type of gear is excellent for abusive drag racing but would be too soft for daily driving and would wear out very quickly. Street gears are mostly manufactured from a harder 8620 steel, which is better equipped for constant use."

0810chp_06_z Strange_engineering_rearend_and_driveline_components_insight S60_rearend 3/10

S60 Rearend"A few years ago, we created the S60, a proprietary casting based on the 12-bolt's architecture that is designed to accept Dana 60 components," Jeff says. "We have cast different centers for vehicles like the A-, G-, and late-model F-body to create bolt-in rearends for several GM applications. The S60 has several advantages over a 12-bolt or 9-inch. It is equal to the 9-inch in strength, and both the 9-inch and S60 are far stronger than a 12-bolt. Also, a lot of OEM Dana 60s were equipped with 35-spline axles, which means you have the option of running either a Traction-Lok, Truetrac, or Locker differential. So if you do not like how a Locker behaves on the street, you can use a very smooth and quiet 35-spline posi unit. The S60 easily adapts to ABS and traction-control systems found on late-model F-body cars and is only about 15 pounds heavier than a comparable 9-inch."

Rearend Fluids
With all the different rearend fluids on the market today, making an educated purchase can be difficult. Jeff says not to be persuaded too much by marketing hype. "We get to see the burned bearings and burned ring-and-pinion sets that are a consequence of many of the special rearend fluids used these days," he says. "We recommend regular petroleum-based oil 85/145W, and while we don't sell oil, we have been very happy with Lucas rearend oil. We do install oil pumps into our Top Fuel rearends, but this is to reduce oil capacity and static weight. As far as fluid that reduces a measurable parasitic drag, we are not privy to any meaningful data."

0810chp_07_z Strange_engineering_rearend_and_driveline_components_insight Axle_picture 4/10

"The two basic types of axles in our industry are thru-hardened and induction-hardened," Jeff says. "There are major differences between a dedicated drag racing axle and a street axle. Drag axles are made from hy-tuf, an alloy composed of low-carbon, high-manganese, high-nickel, high-molybdenum steel content. This type of axle is heat-treated in a vertical furnace to a hardness of 46-48 on a Rockwell scale and is the same hardness from the center of the shaft to the surface of the shaft [thru-hardened], resulting in superior torsional strength and ductility. However, it should not be used for street applications since it is not designed to take the stresses of bumps, potholes, and railroad tracks. On the other hand, street/'strip axles are induction-hardened, a heat treatment that yields an extremely ductile axle. These axles have a high carbon content and achieve a surface hardness of 58-92 on the Rockwell scale. The combination of material and heat treatment creates an axle that can survive the bending loads inherent in street use."


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