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  • How To: Change Your Differential Fluid on a Solid-Axle

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.

Feb 16, 2021
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
Photo 2/11   |   With your vehicle securely positioned, in this case on a rack, place a container under the differential. We started by opening up the oversized inspection/fill port on the AEV differential cover.
Photo 3/11   |   Next, we removed the drain plug on the differential housing.
Photo 4/11   |   Don't be alarmed if your oil comes out dark, as long as it is within the change interval and doesn't smell burnt, and especially if it is your first service after a re-gear, such as was the case with our Jeep. This means that the oil is working to trap contaminants, which is the whole reason you need to do regular servicing. If your fluid comes out frothy, or like a milkshake, that means you have water contamination and could have other issues.
Photo 5/11   |   Upon closer inspection, our lube was still transparent, but we were glad to get it changed over to fresh fluid. We used this opportunity to look through the inspection port with a flashlight and found everything looking as expected.
Photo 6/11   |   Thankfully the Dana AdvanTEK axles include a magnetic drain plug to capture all of the metallic particles. This picture represents about 10,000 miles of use, and this level of contamination is pretty normal from what we have seen for the first differential service on Wrangler JLs.
Photo 7/11   |   With the differential drained, we reinstalled the drain plug, and we removed the fluid level port plug on the diff cover.
Photo 8/11   |   AMSOIL's Severe Gear comes in these amazing resealable Easy-Packs, which make for less mess when refilling. Hard to understate how much easier diff services are when using Easy-Packs and how much we enjoy using them.
Photo 9/11   |   With the seal removed and the nipple cut, we were able to easily fill the Jeep differentials through the huge inspection/fill port on the AEV covers.
Photo 10/11   |   How much do you put in? Well, that's an easy one. Just fill the differential until gear lube starts to drain out of the fluid level port.
Photo 11/11   |   Finally, we re-installed the fluid level port and the fill/inspection port, wiped off the excess oil, and cleaned up our diff and repeated the process on the other axle.
SOURCES
American Expedition Vehicles www.aev-conversions.com
AMSOIL www.amsoil.com

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