Replacing the Front Inner Axle Seals on a '99 XJ Dana 30 Axle. I Made It at TechShop.™




Introduction: Replacing the Front Inner Axle Seals on a '99 XJ Dana 30 Axle. I Made It at TechShop.™

After taking my comanche wheeling in Pismo Beach I noticed a small puddle gathering around the base of both my front tires. Some checking of the brakes and brake lines revealed that the actual culprit was diff fluid leaking from the ends of the axle tubes. My inner axle seals were shot.


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Step 1: Remove the Wheels, Calipers and Wheel Spacers

After jacking up the front end, the first step in the process was to remove the wheels and the front break calipers. Be careful, when removing the calipers, to not let them drop as they could pull loose the break lines. After removing them from the rotos, we placed them on top of the control arms. We also removed my wheel spacers which were holding on the rotors.

Step 2: Remove the Rotors

After removing the calipers and the spacers, the rotors slide right off.

Step 3: Remove the Hubs

The next step is to remove the three bolts holding on the hub. They are in a triangular pattern. Quick side-note - they should be torqued to 75 ft/lbs when re-attaching.

Step 4: Remove the Axle Shafts

After removing the 6 hub bolts from the axle shafts, they should both slide right out. So far, so good. And easy.

Step 5: Remove the Diff Cover

Now that the axles are out it's time to take apart the diff. We removed all of the bolts holding the diff cover on. Straightforward.

Step 6: Draining the Diff

After all the bolts are removed the diff cover must be pried away from the housing. If it was installed properly prior, it should still be held on by the gasket. To do this, we used a flat-head screwdriver and a mallet to open a crack in the gasket and then pry from there. Make sure to have the oil pan ready and don't pry too hard at first to prevent the oil from splashing. After opening the initial crack, we let it drain before prying it away completely.

Step 7: Diff Cover Removed

Once the draining stopped we removed the diff cover completely and placed it to the side next to the axle shafts. In the attached image I have pointed out the diff bearing caps. These pieces hold the diff bearings in which in turn hold the crown gear in place.\

Some special notes here:

1.) Though they look similar, the bearing caps must be re-attached exactly as they were. They are not interchangeable. We placed the driver side bearing next to the driver side shaft and the passenger side bearing next to the passenger side shaft. Also, note the direction in which the writing is facing (in this case reading upwards) so that they face correctly.

2.) When the bolts are refastened, crank them to 45 ft/lbs.

Step 8: Remove the Bearing Caps and Crown Gear

After removing the bearing caps shown in the previous step there is nothing technically holding the crown gear in place accept it's own weight. To remove the crown gear, place a tire iron or pry bar back under the crown gear and pry up and forwards. Try to have someone helping here in case it lurches forward, but in our experience, it moved in fits and starts and was easy to take out in a controlled manner.

Also, note that the diff bearings sit on the crown gear by the weight of the gear. As you remove the gear, these bearings are likely to want to fall off, so be careful to hold them as the gear comes out.

Step 9: Remove Old Seals

After the diff housing is clear of gears it's time to take out the old seals. The easiest way to do this is to hammer them out from inside the tube. We used a breaker bar on the driver's side and a handle from a floor jack for the passenger side. The hammering required isn't that much and once the seals break free, they will fall right out from the inside.

Step 10: Mourn for Old Seals

Once the seals are out you should place them on a flat surface and talk with your friends about how shot they look.

Step 11: Clean the Axle Tubes

With everything out, it's time to do some cleaning!

1.) Wrap some shop towels around a metal rod (we used the handle to the floor jack) and you have yourself an axle tube cleaner. Spray brake cleaner all up in the tube and mop it out.

2.) Spray brake cleaner all in the diff housing and use shop towels to make sure all the dirt and gunk is removed.

3.) Use a wire brush on all your removed bolts. Make them look new! Cleaning the bolts is good preventative maintenance and cleaning the threads will allow the bolts to go back in easier.

4.) Remove the old gasket sealant from the cover and housing. We used a die grinder, but you could also use a straight razor. This is an important step. The cleaner the surfaces are the better the new sealant will seal.

5.) Specially clean the ends of the tubes from the inside of the housing as this is where the new seals will sit.

Step 12: Place the Seals

After cleaning everything, grease the outside edges of the seals and place them inside the housing.

Step 13: Create a Seal Pressing Tool and Press Them Seals

This next step is the hardest. You need to make yourself a tool to seat the axle seals. Take your seal to your nearest hardware store and find something that will fit inside the circumference of the axle seal but is still wide enough to sit on the inside lip of the seal. For us, this was a 1-1/4" piece of PVC joiner.

The original idea, pictured first and second, was to use an all-thread metal rod (1/2") and nuts and washers to push the PVC joiners apart from the inside and force the seals into place. However, it was very difficult to get the contraption and the seals into place correctly. And once we started tightening the bolts, the washers started to give. I imagine that if we had used more washers (3 maybe..) it might have worked, but it was still difficult to get the to sit straight.

What we ended up doing was cutting the rod in half, so we had one half of the original tool, and then getting a 48" long piece of 1/2" metal pipe. We tripled the washers on the single usable end, slid the pipe through the axle tubes over the end of the tool, and hammering the seals into place. The actual tool used is the third picture and hammering into place is the fourth.

Step 14: Seals Are Pressed!

This isn't an actual step so much as a victory lap picture.

Step 15: Tangential Axle Tube Seal Upgrade

While we were down there, I decided to add a bit of an upgrade by inserting axle tube seals. These keep gunk from getting into the axle tubes while wheeling. I assume this also helps the longevity of the inner seals.

Step 16: Replace Crown Gear

Congrats, you're almost done! Now that the seals are in place, you put the bearings back on the crown gear and lift it back into the housing. This is a bit tricky as the bearings will want to come off the crown gear, but hold them on as you lift the gear into the housing. It really helps to have a friend for this step (and for this whole process). Then replace the caps exactly as they were.

Notice the cleaning of the housing surface!! The edge of the cover should look clean and shiny in the same way!

Step 17: Replace Axle Shafts

Now lift the axle shafts back into place. They should slide in freely. If they don't, it probably means the crown gear and bearings are not pushed back into place far enough. This happened to us. But once properly placed, the shafts should go in no problem.

Step 18: Replace Everything Else!

Unfortunately, I did not take pictures from this point forwards, by accident. I'm sorry!

But it is pretty simple from here. Screw the hubs back in and replace the rotos, calipers and wheels. Put gasket maker around the lip of the diff cover and let it set for about ten minutes, until it gets tacky. Then put two screws through the cover, from the outside, as you lift it back onto the housing. Use these two screws to guide the cover back into place. Once it's on, you don't want it moving around as the seal sets, so using these two guide screws allows you to place the cover right the first time. Hand tighten all the cover bolts and then go around in a circle with your ratchet to tighten them all. Wipe away any sealant from the outside and refill your diff with diff oil. We used a pump for this. Pour oil in until it just starts to dribble out, and then replace the filler cap.


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    4 Discussions


    7 years ago

    Great instructable! IMHO the outer seals were the most important thing for the reader to take away from this. They are infinitely easier to change than the inner seals... It's almost a "why didn't the factory do this?" thing! I imagine someone swamping with bad inner seals could just as easily get some aggregate -inside- the differential and possibly lunch the ring & pinion.


    7 years ago on Introduction

    You can also press the new seals in by using a socket and a long extension or pipe. find a socket that fits the seals (cant remember what size i used) and then place it over the seals like you did with the tool you made in the picture and then drive them in gently the same way. Helps to have someone who can watch was is happening to hold the socket or work the hammer to press them in. Great Instructible! Same process on a Wrangler TJ


    Reply 7 years ago on Introduction

    Thanks! From what I read on the web, a 1-7/16 socket is the size to use. We went the homemade route because we thought it'd be cheaper. Dunno if that's actually the case. :) Also, +1 to your comment about having another person. I had a couple of friends helping and it makes all the difference!