Difficulty:  Super Easy - anyone can do this.
Time:  Under 30 minutes
Tools:  Needle nose pliers, socket wrench, rubber mallet, paint scrapper or chisel, Mineral spirits and Hylomar.

Upon returning home from the annual Mendo Rally I noticed that my rear hubs looked a bit like oil based centrifuge art.  The sad part is that I just rebuilt the hubs a few months ago but I suspect that the gaskets I used were not up to the job.  I ordered some new gaskets and felt seals from British Pacific  and got ready to ”unbroke it”.  You can see in the picture below that the leak is still visible even after cleaning it up just below the 6 inner drive flange bolts.

SETTING UP
Although it is not required to lift the vehicle to remove the drive flange, it’s helpful if you can lift the side you are working on causing the oil in the axle to tip away from the soon-to-be open hub thus reducing the amount of wasted oil and mess.  Regardless of lifting, place the vehicle in gear and engage the hand brake.  You’ll also want to have some paper towels on hand and spread some news paper around the tire you’ll be working on.  Before you proceed, be sure to remove any excess dirt and oil from around the drive flange.

It is also worth mentioning at this point that leaking on the backside/inside of your wheel is probably not the drive flange gasket that is being outlined below.  You’ll probably want to check your hub oil seal and break cylinders.

STEP 1: REMOVAL
Remove the six bolts from the drive flange and drop them into a container.  Make sure they all have lock washers.  Spray with some mineral spirits (available at your local paint/hardware store) and put them aside.

Get your paper towels ready and pull out the drive flange.  If it gives you some resistance go ahead and use a paint scrapper and a rubber mallet and GENTLY help separate it from the hub.  Once removed, oil will begin to ooze out - jam a paper towel in the hub to stop the leak and then clean up the leaked oil from your wheel and surrounding area. Pull out the drive flange (which will be attached to a axle shaft) and lay it on the newspaper.  Also take a few minutes to clean off the hub of any oil, dirt and old gasket.  The hub face should be fairly smooth and clean to ensure a snug seal with your new gasket you’ll be fitting later.    If you have a vise, wrap the axle in a rag and snug it up.  Go ahead and clean off any excess oil and dirt from the axle and drive flange using more mineral spirits and a paper towel.

 STEP 2: DISASSEMBLY
Interestingly enough it seems that some folks really seem to have a tough time removing and refitting the hub cap.  Grab a chisel, slip it behind the hub cap and gently tap towards the axel.  Do this going round the hubcap 2-3 times and it will slowly lift off and pop-off.If it came off super easily then buy a new hub cap to ensure a better seal.

Below you can see the drive flange with the hub cap removed.  The castle nut (named such because it looks like a castle) is held in place by a split pin (AKA: cotter pin) which should be splayed apart at the end.  Using needle nose pliers, attempt to straighten the pin so it can be removed.  If it breaks or is in poor shape just grab another from your local hardware store for around $0.05.  The pin can always be pulled out using a bit or force by yanking on the other end.  Once removed the castle nut should easily come off, followed by a metal washer.  Use the needle nose pliers to pull out the felt seal and throw it away. Gently tap the drive flange off the axle shaft using a rubber mallet.

Below you can see all the parts laid out with the new gasket and felt seal.

Drop the drive flange, castle nut and metal washer into a container and spray them with mineral spirits and let them soak for a few minutes, scrub them a bit with a wire brush and then clean them off using some paper towels.  This is a good time to inspect your axle by making sure the teeth at the end are straight and  not ripped up at all.  Replace the axle shaft if needed.

STEP 3: ASSEMBLY
Place the drive flange back on the axle followed by the felt washer, metal washer and then the castle bolt.  Below is a picture of it all together before being tightened.

Do not over tighten this - you can see below that the top of the felt washer is still visible when tightened.  The hole for the split pin should not be too far above the castle nut.

Apply some brake grease around the inside of the hub cap to help create a good seal.

Using a pipe or appropriate size or hub nut tool and a rubber mallet gently tap the hub cap back on.  No need to hit hard or else you will warp the hub cap and it won’t make a nice seal. 

STEP 4: GASKET
It is at this point I will HIGHLY recommend that you buy some Hylomar Gasket Sealer which is now available at many auto part stores.  There is nothing like Hylomar - it’s the only game in town as it never dries and creates a GREAT seal.  Don’t skimp on this - use Hylomar. 

Spread your gasket on a disposable clean surface (cardboard works fine) and give it a clean coat of Hylomar on both sides.  Be careful not to tear the gasket when flipping it over.  I also recommend NOT wearing gloves for this.

Place the gasket on the drive flange (there is no up/down face so just stick it on there) and make sure the holes in the gasket are aligned with the holes in the drive flange.

STEP 5: REFITTING
Put the axle back into the hub trying to align the holes before you push it all the way in.  Remove the paper towel and push it all the way in.  Again, make sure the holes are all aligned and re-align if needed.

Tighten all six bolts and lock washers snugly but not too tight.  Wait about 5 minutes and then tighten them to the point where you make the “ummmph!” noise  which tends to be tight but not massively tight.

There you have it - hopefully it fixed your leak.   Be sure to top off your axle with oil while you’re at it.  ;o)