If you have a 4WD Wrangler, changing out the differential oil is a must and it is much easier than changing out your engine oil.By Jeffrey Smith – November 17, 2015
Contributors: wayoflife

This article applies to the Jeep Wrangler JK (2007-Present).

If you have a 4WD Jeep Wrangler, you should be aware that changing the differential oil is part of your routine maintenance for your vehicle. Don’t be fooled into thinking that this has to be done by a professional or at the dealership. Unfortunately, differential oil is a bit pricey compared to regular engine oil; however, the dealership may charge up to three times as much as you can find it on your own at just about any auto parts store. You will also be charged a small fortune in labor costs for a job that shouldn’t take you more than 30 minutes to do yourself. Changing the differential oil is about as easy as any job you can do on your Jeep. You don’t need any skills or special tools at all, and you will be pleasantly shocked at just how much money you will save by doing this on your own. The most difficult aspect of this job in fact is simply deciding which brand to use and whether or not to go with traditional Dino or a synthetic.

Materials Needed

  • 3/8″ drive ratchet with short extension (2-3″)
  • Catch pan for used oil
  • Brake cleaner
  • Shop rags
  • Torque wrench
  • One gallon of at least 75W-90
  • Fully synthetic or an additive with Dino oil (for limited slip differential setup)

Please dispose of used oil responsibly. Most quick lube stations will take in used oil and dispose of it for you at no cost.

Step 1 – Start with the front axle

You will not have to jack up or lift your Jeep for this job. The plugs should easily be within reach from the ground with plenty of clearance to work with. It is recommended that every other oil change, or if you have been running through deep water, to remove the differential cover plate and inspect and clean the gearing mechanisms. Otherwise, just draining and refilling the oil is all that is needed.

  • Using just the ratchet and extension without a socket, remove the fill plug from the differential cover.
  • The fill plug has a recessed square hole into which the end of the 3/8″ extension will fit.
  • Remove the fill plug, this will allow faster draining when the drain plug is removed.
  • Have your catch pan located underneath the differential and locate the drain plug on the bottom portion of the differential.
  • The drain plug has the same recessed square port for the ratchet extension.
  • Remove the lower drain plug and let all the oil drain out into the pan.

Step 2 – Inspect the drain bolt

The end of the drain bolt is magnetic in order to collect small metal shavings from normal wear and tear on the gears. If you find any large chunks attached, you need to remove the differential cover and inspect your gears. There is likely some damage. At the same time, you will also want to run a magnet through the pan with the old fluid to see if there are any large chunks of debris that came through the hole. This is an indication that you have some issues in the gears that you will need to have addressed and remedied. Before you replace the drain bolt, clean it up nicely with some brake cleaner and wipe it down with a rag.

Step 3 – Replace drain bolt and re-fill differential

  • After you have cleaned up the drain bolt, replace it and torque it to 25 ft/lbs per inch.
  • Add new gear oil to the fill hole.
  • With stock covers, you only need to fill it until it starts weeping out of the bottom of the fill hole (about 1.35 quarts).
  • Do not over-fill.
  • If you are using conventional Dino, you will need to add friction modifiers with the limited slip differentials.
  • If you are using purely synthetic gear oil, you need no additives.
  • Replace the fill plug and torque it to 25 ft/lbs, as well.

Step 4 – Repeat the process for rear differential

The process for draining and re-filling the rear differential is exactly the same with one minor difference. The rear axle will hold about one additional quart (2.375). Make sure to thoroughly check the drain plug as well as the used oil for any large chunks, and clean the drain plug as you did the front. Do not be concerned if the rear differential fluid is much darker and dirtier than the front, as this is quite normal.

Figure 5. The only difference with the rear from the front is that the rear hold more fluid.

Featured Video: Changing Jeep Wrangler Differential Fluid

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