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Trussing An Axle The Right WayDon't Let Your Axle Fall Down From the March, 2012 issue of 4Wheel & Off-Road By Fred Williams Photography by Fred Williams
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Yeehaw! It’s all fun and games... Yeehaw! It’s all fun and games until the landing. That is when the ground pushes up on your axletube via tires and wheels while your truck pushes down via body, frame, and suspension. Eventually something might give in. Imagine your 4x4 equipped with larger-than-stock tires ripping across the desert or mud bog when all of a sudden a hidden berm, log, or ditch sends you skyward. You land with a crash and likely do one of two things: get out and check for damage, or spin a U-turn and do it again because it was so much fun. Either way you may want to consider just how much abuse your axles are taking. Axlehousings often bend because... Axlehousings often bend because of constant pounding from going fast, landing from big jumps, or hitting a trail obstacle (rock, tree, ditch) at speed. An axle truss must gusset the axletube against this by forming a long low triangle away from the axletubes such as this unit on the rear of the infamous Herbst Land Shark Class 1 Buggy. When OEMs source an axlehousing they have two priorities. Will it do the job required by the stock vehicle, and at what cost? When we four-wheelers get a hold of an axle we inevitably put greater stresses and abuse on it than the OEMs or axle manufacturers ever required. One way to care for your gear-spinning, shaft-protecting axlehousing is to install a truss. A truss is a simple or elaborate steel structure that gussets and supports the axletubes in such a way as to deter bending from excessive use and abuse, something we wheelers call fun.  Axle trusses can be very elaborate...  Axle trusses can be very elaborate and serve multiple purposes. This rear axle under our Project Fun Buggy uses a Synergy Suspension universal truss over the axle for strength and upper link mount attachment. The rear truss supports the axle from bending rearward while also adding a mounting point and protection for a steering hydraulic ram. Note how the centersection of the rear truss can be removed to gain access to the axle gears and differential.  A small axle such as those...  A small axle such as those found under a Suzuki Samurai can greatly benefit from an axle truss for support, especially if you wheel hard, drive fast off-road, and carry a lot of gear. This custom truss was built by Randy Ellis Design. When you’re welding to thin sheetmetal housings like this, you need to use care to not warp it with too much welding heat. It’s important to use a jig to hold the housing straight, weld with low heat, and move around to weld in increments.  The axletubes are inclined...  The axletubes are inclined to bend up or backward, but the truss can be on the front or bottom as well as the back or top. This Toyota front axle (bottom) actually has four different truss systems: a lower, front, and top truss as well as small axle gussets attached to the steering balls. All of these help reduce bending in different directions. Notice how the rear axle truss (top) runs all the way to the ends of the axletubes for support.  An axle truss makes a great...  An axle truss makes a great upper link mount for a four-link suspension such as this one built by All-Pro Off-Road for our Ultimate Adventure FJ Cruiser. However, it could work better against bending if the truss ran the length of the axletubes.  Jeep JK Wranglers are earning...  Jeep JK Wranglers are earning a bad reputation for bending axlehousings after aggressive abuse. Many companies offer weld-on gussets for the C’s to defend against movement from big tires and off-road use.  Here is another option for...  Here is another option for a JK truss: a complete set of half-tubes that are welded over the axletubes from Synergy. These add tube thickness but require a complete teardown, bracket removal, and rebuilding of the axle to install. Also they do not support as well as a full truss.  Truss mounting location is...  Truss mounting location is an important consideration. Old-style bolt-on trusses mounted below the axletube often hinder ground clearance. Many current aftermarket trusses are being built on the tops of axles such as these from Artec, and though this doesn’t hinder ground clearance it can hinder uptravel. Now you have a truss that may crash into engine, exhaust, and fuel tanks under full suspension compression, in turn requiring a taller ride height. Every position has its pros and cons; you’ll have to decide which is best for you.  Another consideration is weight....  Another consideration is weight. Trusses are trendy right now, and there is no denying that a well-built axle truss like these Camburg units are sexy, but a lot of axles are just fine without the additional unsprung weight from welding on a truss. Every ounce of weight robs power, and unsprung weight (everything below the springs) needs to move quickly over obstacles, so reducing weight is important. When building or purchasing a truss consider using a thinner-gauge steel if possible.  We recently came across a...  We recently came across a prototype front axle truss from Synergy that is specifically a suspension mount and not a truss against axle bending. This design allows a suspension link to be mounted above a Dana 44 cast centersection. It also ties the tubes together for strength, has a pinion mount to lessen the chance of the tubes spinning, and is low-profile for greater uptravel than some giant trusses.
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