Click for Coverage
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler
Subscribe to the Free

Trail Gear Rock Assault Axle Housing Axle Swap

Posted in How To: Transmission Drivetrain on May 1, 2009 Comment (0)
Share this
Overall, the standard rear Rock Assault housing measures 51 3/8 inches from mounting flange to mounting flange. Each weighs just 54 pounds, includes a drain plug, and comes unpainted and ready for service. Other options like spring perches, shock mounts, and diff breathers are also available through Trail-Gear.

When Trail-Gear introduced a whole new concept in axlehousing design, we took notice. After all it's not every day that innovation merges with a proven design like the solid axle. However, at the time we lumped the new offering into the high-dollar category thinking, "sure it's cool, but it probably costs an arm and a leg to purchase." Then about a month later we stumbled upon the price tag online. Would you believe $399? We had to do a double take when we realized that this axlehousing is actually affordable. So we decided an in-depth look was in order.

The exclusive design features axletubes that are offset above the housing centerline of the differential, thus making the inner axleshafts ride closer to the bottom of the tubes rather than in the center.The results are a gain of 3?8 inch of ground clearance under the axletubing. In addition, the stamped-steel centersection offers an additional 3/4 inch of clearance over the factory housing. The axletubes are made from 1/4-inch-thick DOM tubing instead of formed sheet steel and the differential mounting surface is made from 1/2-inch steel plate to ensure studs remain where they should, even under heavy loads.Trail-Gear tells us that each and every Rock Assault housing is precision aligned during and after construction using state-of-the-art, 3D digital imaging equipment. We think this new housing is the cat's meow for all '86-'95 Toyota Pickup or 4Runner owners who want increased durability that won't break the bank. Follow along now as we highlight the swap procedure as performed by Trail-Gear at its Fresno, California, headquarters.

While the new axlehousing was being installed, our donor rig's factory third member was being treated to a traction makeover. We figured since we were going ultra low-buck with this project, a full spool from Randy's Ring & Pinion was the best option. At just $151.62 (at time of print), this is the most economical way to lock a trail-only Toyota rear axle.

PhotosView Slideshow

Custom Rock Assault Options
This is the Creeper Breather by Trail-Gear. This differential breather kit is favored by professional rock racers because it prevents dirt, debris, and water from entering the axlehousing. The accordion-shaped rubber part expands and contracts to accommodate increase or decrease in housing pressure. No hoses to route and fits snugly on all Toyota Pickup/4Runner solid-axle housings (front or rear).

Fill/Inspection Cap
This extra large differential fill and inspection cap was designed to allow quick access forinspecting the ring gear and/or filling the Rock Assault axle with oil. It features a 1.5-inch-diameter access hole that fits a threaded aluminum cap with rubber O-ring perfectly. Installation requires cutting a hole in the top of the differential housing and welding on a threaded bung. The kit can be ordered loose as a do-it yourself install or it can be ordered as part of the Rock Assault housing at the time of purchase.

Rock Assault Upper Link Mount
Also available for a rear Rock Assault axlehousing is this trick upper-link-mount kit. Designed to accommodate 1.25-inch Currie-made Johnny Joints, this upper link mount can be ordered loose as a do-it-yourself piece, or if desired it can be ordered installed on the Rock Assault housing from the very start.


Fresno, CA 93727
Yukon Gear


Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results