Torque Arm To The RescuePosted in How To: Transmission Drivetrain on January 1, 2011 0) (
If you own a vehicle equipped with rear leaf spring suspension, you have probably felt wheel hop or axlewrap during hard acceleration or while climbing a steep obstacle in the dirt. The condition is a result of the leaf springs flexing into an "S" shape while torque is being applied. Typically, the effect causes the axle to move up and down rapidly as the leaf springs twist and recoil in an attempt to maintain their intended flat or arched shape. Axlewrap is not good for the life of drivetrain components, including the rear driveshaft, transfer-case output, and rear axlehousing. It can also adversely affect the life of leaf springs, as excessive axlewrap usually bends or flattens out the arch of the leaf pack. The problem is common to all rear-wheel-drive vehicles with leaf springs. High horsepower tends to amplify the problem, and longer leaf springs with fewer individual leaves per pack are more susceptible to the problem.
In all cases, axlewrap has a negative effect on trail performance, as it reduces traction and places added stress on the internal components of an axle assembly. That's why WFO Concepts of Auburn, California, developed a universal torque arm designed to eliminate axlewrap. Follow along as we highlight the installation process as performed by the skilled truck builders at WFO Concepts on an '05 Nissan Frontier pickup truck.
How It Works
Just as we suspected, the new torque arm assembly eliminated axlewrap altogether. By doing so, the setup resolved a transfer-case output seal issue that our donor truck's owner was fighting with. The problem is common to late-model Nissan vehicles with modified suspensions. When a Frontier, Titan, Xterra, or Pathfinder is lifted, the rear driveshaft operating angle becomes more acute. Due to the fact that no true slip-yoke eliminator exists for the Nissan transfer case, the seal in the slip yoke assembly is exposed to additional vertical movement of the rear driveline. The factory seal was not designed to handle these additional forces. The result is premature seal failure and an oily residue covering everything under the back half of the vehicle-which can quickly result in a transfer case failure.
Currently, Nissan does not offer replacement parts for these transfer cases. Instead, the dealership advises replacement of the entire unit-a costly fix, to say the least. Luckily for our donor truck's owner, we had the old stock Nissan transfer case out of the Mega Titan sitting around collecting dust. WFO installed it for us prior to adding the torque arm assembly.
We feel that it's also important to mention the fact that our donor rig had modified rear leaf packs that were more susceptible to axlewrap than most stock arrangements. The main overload leaves were replaced with a set of Deaver mini-packs when the tuck was originally lifted. This setup provides a much softer ride quality, but also allows the axle assembly to twist more easily under torque. Thanks to WFO Concepts and their stout torque arm assembly, our donor truck's owner will never have to deal with the negative affects of axlewrap again. Our tester reported that his truck felt quicker off the line after the installation of the torque arm, which makes sense because more power is reaching the ground instead of being wasted on twisting the axlehousing against the leaf springs. The vehicle's ride quality was not affected by the modification, nor did the new part contribute any new noises. Overall, we were impressed with the results of this project.