How To: Change Your Differential Fluid on a Solid-Axle
Regular differential servicing is the key to long life and performance for your axles and gears.
Changing gear oil is one of those often-forgotten maintenance items on our rigs. Whether it's the smell of gear oil, the disposal of gear oil, or the mess that can sometimes come from popping a cover, many people seem to leave their differential fluid in way too long.
The differential oil's job is thermal regulation and lubrication, protecting the bearing and gear surfaces to withstand the shock loads coming from the drivetrain. Neglecting your diffs can lead to lack of lubrication, premature surface wear of bearings and gears due to metal-to-metal contact, and excessive heat that will ultimately lead to nasty sludge and eventually failure, in a probably not-unspectacular way. Of course, all of this is avoidable by simply servicing your differentials, an easy process we'll walk you through.
One product we recommend that will make changing your gear lube easier, quicker, and less messy is an aftermarket differential cover. These covers, like the American Expedition Vehicle (AEV) covers on the Jeep Wrangler JL in this story, aren't only for protection on the trail with its reinforced bottom edge; they also have a number of features like a large fill/inspection port and a fluid level port to keep things easy. This will prevent you from having to remove the cover or having to replace the gasket.
We also recommend using a high-quality gear lube, like AMSOIL's 100 percent synthetic Severe Gear, which comes in the company's awesome 1-quart Easy-Pack packaging and, incidentally, won't make your garage smell like a lube shop for weeks on end. Available in either 75W-90 or 75W-140 weights, AMSOIL's Sever Gear is engineered with high film strength for the most extreme use cases. AMSOIL says Severe Gear reduces friction, protects against wear, excels in extreme temperatures, and outperforms conventional gear oils. Some vehicles require the addition of a friction modifier for their limited-slip differentials to work correctly, so be sure to know your vehicle's specific requirements before starting the job.
While the frequency of differential fluid changes can vary by manufacturer and lube type, we typically change ours every 15,000 miles—or sometimes sooner if the differentials have been submerged in water or have been subjected to severe duty cycles, such as towing or hardcore trail riding. Synthetic oil will allow for extended intervals, but just to play it safe we still keep to our schedule, whether our diffs need it or not.
One last item of note it to know is how much gear oil your differential will take and have enough on hand prior to starting your servicing process. Because fluid sitting in the tubes is unlikely to fully drain out, be aware that you are unlikely to use as much fluid as the manufacturer capacity states.
So how hard is it to swap out your gear oil? Let's get started