Disclaimer: This write-up is
as a basic how-to article. Obviously, if you've swapped axles in your
Jeep and you're running something other than stock, you probably know
how to change your diff fluid. For everybody else, here goes.
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
etc are all similar.
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
- torque wrench (nice to have, but not required)
- brake/carb cleaner
- wire brush
- gasket scraper
- drain pan
- funnel or other device to refill the differential
The first step is to
prepare your work area. Gear oil is smelly stuff and you definitely do
not want it on your driveway or garage floor. I lay down newspaper and
keep plenty of paper towels and cat litter handy. Begin by inspecting
the 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.
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
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 remaining 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.
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 avoid using any sharp metal tools like screwdrivers to remove the
gasket. 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
body work, 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
you've previously installed a
magnet on the cover of have a magnetic cover, inspect it for chunks of
metal. Small particles are normal, but anything large is cause for
Once you've removed
the old gasket, use paper towels to clean as much remaining oil and
anything else that might have found their 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 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.
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 require a friction modifier for limited
slip clutches, now is the time to add it.
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. If you have a limited slip diff, follow any
directions that come with the friction modifier, but typically they
recommend you drive a number of figure 8's. Personally, I raise first
one side of the Jeep and then the other to allow the fluid to settle
within the housing. I then check the fluid level and add as required.
it. You're done. Now take
your smelly old oil to your local recycling center.
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