Changing Your Jeep’s Differential Fluid Guide

Time needed: 1 hour and 30 minutes

When it comes to maintaining your Jeep’s performance and ensuring its longevity, one crucial aspect that often gets overlooked is the differential fluid. The differential fluid plays a vital role in lubricating and cooling the gears inside the differential, which helps to reduce friction and wear. Regularly changing your Jeep’s differential fluid is a simple yet essential maintenance task that can save you from costly repairs down the road. In this comprehensive guide, we will walk you through the process of changing your Jeep’s differential fluid, step by step, ensuring that your Jeep continues to perform at its best.

This write-up describes the basics of changing your Jeep’s differential fluid, whatever model it might be. I took photos as I worked on my Dana 30, however, a Dana 44, Dana 35c axles, etc are all similar.

Why is Changing Your Jeep’s Differential Fluid Important?

Your Jeep’s differential is responsible for transferring power from the engine to the wheels. It contains a set of gears that allow the wheels to rotate at different speeds while turning corners. The differential fluid not only lubricates these gears but also helps to dissipate heat generated during operation. Over time, the differential fluid breaks down, becomes contaminated, and loses its effectiveness. If left unchanged, it can lead to increased friction, excessive heat, gear wear, and eventual damage to the differential itself.

Step-by-Step Guide to Changing Your Jeep’s Differential Fluid

1. Tools and Materials You Will Need

   This isn’t difficult and it’s certainly not beyond the capabilities of most people. If you can change your oil, then changing your diff fluid is easily within reach. I use the following tools:

   • paper towels
   • rubber mallet
   • wrench
   • torque wrench (nice to have, but not required)
   • brake/carb cleaner
   • wire brush
   • gasket scraper
   • drain pan
   • funnel or another device to refill the differential
   • gloves
   

2. Prepare Your Work Area and Jeep

   Gear oil is smelly stuff and you definitely do not want it on your driveway or garage floor. I lay down the newspaper and keep plenty of paper towels and cat litter handy. Begin by inspecting the differential cover and bolts. If anything is damaged beyond repair, now is the time to head to the parts store to buy replacements. I had a couple of bolts that lost a match to some rocks and were ground down. Of course, I didn’t discover this until late Sunday afternoon when most stores were closed. Oh well, better planning next time.

   

Lift Your Jeep

Use a floor jack to lift your Jeep off the ground. Place jack stands underneath for added stability and safety.

Locate the Differential

The differential is typically located between the rear wheels of your Jeep. Consult your owner’s manual if you’re unsure about its exact location.

3. Remove the Fill Plug From the Cover

   The plug is typically metal but the Dana 35 uses a rubber plug. After you’ve removed the fill plug, remove all of the cover’s bolts leaving one of the top bolts. The gasket will hold the cover in place. Loosen the remaining bolt but do not remove it yet. This will keep the cover from falling and (hopefully) avoid making a mess when you break the sealant.

   You can use a screwdriver to carefully pry the cover off, but I use a rubber mallet to whack the side of the cover. Have a wide container under the differential to catch the gear oil that will come pouring out. Once you’ve broken the seal, allow the majority of the fluid to drain. You can then remove the retaining bolt and pull the cover off. Use a lint-free cloth, flushing oil, or light engine oil to clean the housing. Do not use water, steam, kerosene, or gasoline. Use a rag or paper towels to cover the differential.

4. Inspect the Cover for Rock Rash

   If it’s not too bad, you can usually use a hammer to beat it back into shape if it’s been bent. Remove the old gasket material from the bolts, cover, and housing mating surfaces. I use brake cleaner to clean the cover and any stubborn gasket material. Follow the directions on any solvent you use. It’s flammable so no open flames. Watch out for campfires, heaters, cigarettes, etc. If you forget, changing your fluid is the last thing you’ll be worried about. To protect your axles from damage I strongly recommend you to change your stock cover to the best diff covers for Jeep.

5. Removing The Gasket

   Try to avoid using any sharp metal tools like screwdrivers. These are liable to damage the mating surfaces. I use a cheap plastic blade to scrape off the old gasket. I think it’s designed for bodywork, but it works for this purpose. It’s good for about four changes before it gets too chewed up, but at fifty cents a piece, I’m not complaining.

   If you’ve previously installed a magnet on the cover or have a magnetic cover, inspect it for chunks of metal. Small particles are normal, but anything large is cause for concern.

6. Mount the Differential Cover

   

   Once you’ve removed the old gasket, use paper towels to clean as much remaining oil and anything else that might have found its way inside the housing. Run a bead of your favorite brand of RTV around the mating surface of the cover. The Factory Service Manual (FSM) calls for a 1/4″ bead but I tend to use a little more. I got a little sloppy this time, but hopefully, you get the idea. Do not allow the RTV to set for more than five minutes before mounting the cover or you’ll need to remove it and reapply a new bead. Mount the cover being careful not to smear the RTV. Torque the cover bolts to appropriate specs.

7. Adding Gear Oil

   

   I usually allow the RTV to set for an hour or so before adding gear oil, but follow the directions on the tube. If your particular axle requires a friction modifier for limited-slip clutches, now is the time to add it.

   When you’re ready, add your axle’s favorite flavor of gear oil. You can use a pump or funnel to pour the fluid in through the fill hole. Somewhere in my travels, I picked up a nifty device the screws onto the bottle and has a hose long enough that’ll reach the diff. It also has an on/off valve. Fill the diff until fluid starts dripping out of the hole. Replace the plug.