The axles are probably the most abused components on our 4x4s. We regularly overload them with heavy payloads and trailers, expect them to survive with larger than stock tires, sink them in deep mud and water, and in most cases, we rarely ever maintain them. It’s not at all uncommon for an axle to go 100,000 miles or more without so much as an oil change. We usually only pay them any attention when something goes really wrong. So in the spirit of sticking with the no-maintenance theme, there are a few tips, tricks, and upgrades you can implement to increase the durability and service life of your axles.
Got an axle problem not discussed here? Drop the Techline department a note at firstname.lastname@example.org with “Techline” in the subject line.
Axlehousings that have been severely overloaded or abused will leak from where the tubes are pressed into the cast centersection and from the plug welds. Companies such as Artec Industries (artecindustries.com) and RuffStuff Specialties (ruffstuffspecialties.com) offer weld-on trusses to reinforce the axlehousings and help prevent this kind of failure.
Oil oozing from a front axletube at the end forging means that the inner axle seal is shot. Unfortunately, full axle disassembly is required for repair. Companies such as Alloy USA (alloyusa.com), Seals-It (sealsit.com), and TEN Factory (tenfactory.com) offer outer axletube seals that can help keep the dirt and grime out of the axletube and extend inner seal life. This Dana 60 is also clearly suffering from a massive steering U-joint failure.
Front axleshaft U-joints are very prone to wear and failure. Rust dust deposits around the U-joint caps is a sure sign that the lubricant in the joint is gone and the U-joint needs to be replaced. This broken U-joint has created enough slop for the axleshaft ears to make contact. Non-greaseable steering U-joints like Spicer (spicerparts.com) Life Series joints tend to have a stronger body and better seals than their greaseable counterparts.
Companies like Alloy USA, CTM Racing Products (ctmracing.com), and OX Off Road (ox-usa.com) offer heavy-duty replacement steering U-joints for popular axle applications.
Stock axleshafts usually aren’t enough for larger tires, more power, increased traction, and abusive drivers. Heavy-duty replacement axleshafts are available from companies like Alloy USA, CTM Racing Products, Dynatrac (dynatrac.com), G2 Axle & Gear (g2axle.com), RCV Performance Products (rcvperformance.com), and others.
Thick black grease flung in the front wheelwell of your independent front suspension (IFS) 4x4 is a good indicator that one of the CV axle boots is torn. Inspect the boots regularly for cracks and tears. Replace the CV or the entire halfshaft if the joints become contaminated with dirt. Most auto parts stores offer complete new or remanufactured halfshafts at a reasonable price so it’s usually not worth the time and effort to rebuild your halfshaft. RCV offers complete heavy-duty halfshafts for some popular IFS 4x4 applications.
If you destroy an IFS CV or other unit bearing-style front axleshaft out on the trail, don’t be too quick to pull the whole axleshaft and limp out. Most front unit wheel bearing assemblies require the stub shaft to be installed and torqued to spec. Disassemble the halfshaft or axleshaft and reinstall the stub in the bearing assembly prior to limping home.
Oil leaking down the bottom of a rear brake backing plate will typically require rear axle seal replacement. In most cases, the oil will have contaminated the brake shoes or pads. They will need to be replaced as well. Oil-soaked brake shoes or pads cannot be cleaned and will not properly stop the vehicle.
The pinion bearings spin several times faster than any other bearing in an axle assembly. They are more susceptible to contaminated gear oil and wear. Worn or improperly preloaded pinion bearings will emit a high-pitched whine. If not corrected quickly, the gears can become damaged as well.
A deeper groaning sound and vibration coming from the axle assembly usually means the carrier or axleshaft bearings are worn. Failure to replace worn carrier bearings will eventually result in a damaged ring-and-pinion and carrier. Worn axleshaft bearings can lead to a damaged axleshaft or axlehousing.
Banging, whirring, and clunking noises coming from an axle assembly usually means the ring-and-pinion or carrier have failed or have not been installed properly. You’ll want to avoid driving any distance at speed. The axle could unexpectedly lock up from broken and binding bits floating around inside.
Crossing deep water and mud in your 4x4 can lead to contaminated axle fluid. Water-infused gear oil looks like a milkshake and will lead to prematurely worn axle internals. Flush and replace the fluids regularly if your favorite type of four-wheeling involves H2O. Switching to a synthetic gear oil such as AMSOIL (amsoil.com) can help keep everything well lubricated in adverse conditions. Extend the axle breather lines above your planned water crossing depths to help prevent water intrusion and contamination.
It’s always a good idea to inspect the gear teeth and other internals when changing the fluid in your axles. Excessive metal flake in the oil is a good indicator that something is awry. You can throw a dial indicator on the ring-and-pinion assembly to make sure the gear backlash is still in spec. Harbor Freight (harborfreight.com) offers a low-cost dial indicator that won’t break the bank.
After sealing and installing the differential cover or third-member, trim away any gasket overhang. Sometimes rock contact can pull on an untrimmed gasket and create an oil leak.