F150 Rear Differential Oil Change*
Ford F150 4x4 with 4.6L V-8, 4R70W 4spd
electronic automatic (code U in doorjam),
3.55LS axle. Axle service interval
30,000 miles or 24 months according to
these instructions at your own risk.
Tools/Parts needed for the job:
- Safety glasses
- Rubber gloves
- 3/8 Ratchet, and 1/2 socket
- Cleaning solvent such as Brakekleen
- Drain pan
- Small funnel with hose
- Rags/paper towels
- 3 quarts Redline 100% Synthetic
gear oil (Ford specifies only
- Replacement differential cover
- Gasket type blue silicone sealer
- scraper blade or flat wide chisel
- flat blade screwdriver
wear safety glasses while under the
vehicle for eye protection as there's
lots of dirt and grime under there just
waiting to drop into your eyes.
Time to do job:
- Wait until the vehicle has cooled
off for at least 1/2hr if you've just
driven it to avoid getting a "hot
oil treatment"... burns hurt!
- Position the drain pan under the
rear diff cover.
- Remove or loosen all the cover
bolts using the 1/2 inch socket
ratchet. Note the position of the two
tags on the bolts.
- Using a large flat blade
screwdriver pry the bottom of the cover
up slowly. When most of the fluid has
run out pry the cover off the axle. The
old fluid was really black and dirty.
- Use a solvent or brakekleen to
clean the diff cover in combination
with rags or paper towel.
- Use a flat edge scraper or chisel
to remove any old excess silicone
sealer. My factory sealed diff didn't
even use a real gasket, only black
- When the cover is clean move to the
axle and using your finger or a spatula
and remove as much old oil as possible.
There is a small pocket in the diff
that holds half a cup of oil in the
bottom. Try to slosh it out or use a
few paper towels to absorb it. Wipe off
oil anywhere you can get to on the
gears and walls inside the axle.
- Now clean the gasket surface on the
axle with a scraper and some steel wool
to get it clean. Finish off with
solvent on a rag or paper towel to
remove any trace of grease/oil on the
- Clean the diff cover in the same
- When the surfaces have dried, apply
a bead of silicone gasket to the cover
and to the axle gasket surface.
- Apply the new gasket and press it
down gently to spread the silicone
- Wait 10-15 minutes for the silicone
to skin over.
- Apply the cover to the diff, insert
all the bolts and tighten them lightly.
There is no specific order. I started
at the bottom, moved up the sides, and
finished at the top bolt. I believe the
Haynes manual states 30-38ft/lbs.
Tighten the bolts all one more time to
spec, then check each one for
- Insert a 3/8 ratchet into the drain
nut and remove it.
- Clean any metal shavings &
sludge of the plug.
- Insert a small funnel and tube into
the hole or use a transfer pump
(easier, less messy).
- Fill the case with just under **3 Quarts (5.7
pints spec) for F150 and Expy rear
axles, F250 are more. Or fill the axle
on level ground until oil starts to run
out of the filler hole. I call gear oil
"yummy lube" because it
stinks so bad.
- Replace the drain plug. Loktite is
optional on the threads of the plug.
- Wipe any spilled oil.
- Clean up.
Some Ford techs recommend not using the
Ford spec 70W140 synthetic due to it not
being able to absorb water and possibly
leading to corrosion and failure of
parts within the axle assembly. For that
reason I chose Redline 75W90. Please
note this is not my recommendation. Do
so at your own risk!
Installing a replacement gasket is
also optional. Some prefer blue silicone
only but it needs to be tacky
(>15mins wait) before putting parts
together or the silicone will squeeze
out from between parts resulting in