When someone with a Ford F-150, Ford Expedition or
Lincoln Navigator comes into the shop, complaining
about a grinding sound from the fourwheel drive,
there’s a common diagnosis: a bad vacuumactivated
front axle hub actuator. The internal diaphragm on
these parts wears out from regular use, or cracks from
lack of use, as well as poor internal lubrication. The
grinding happens when the splined actuator doesn’t
have the vacuum it needs to fully engage the axle shaft.
Eventually the vacuum leak expands, preventing the
system from working at all.
Connection Correction
A creative alternative to stock hub actuators
Knowing how commonly they fail, we made a direct
replacement, but our engineers wanted to nd
another solution. They wanted a dierent method for
activating the hub locks. The thing is, with the actuator
sandwiched between the hub and axle, designing a
whole new system would be impractical.
However, most people assume that locking the hubs
also engages the four-wheel drive. That’s actually
not the case. They’re two dependent, but separate,
operations.
The hub actuators connect the axle shaft to the
wheel hub automatically when 4WD is selected. More
“This is a good example where we were able to give vehicle owners
more freedom to x their vehicle however they choose.”
– Steve Butcher, Product Manager (Undercar)
Dorman Products
600-405
Ford Expedition 2015-03, F-150 2015-04,
Lincoln Mark LT 2008-06, Navigator 2015-03
OEFIX_CaseStudy
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accurately, they disconnect the axle and hub when the
4WD system is not engaged, reducing driveline loss
caused by spinning an otherwise non-rotating axle.
So, while the hubs must be locked for 4WD to be
engaged, they can also be locked when the vehicle is in
2WD. Doing that sacrices a small amount of driveline
eciency, in exchange for greater dependability, by
eliminating the troublesome functionality.
With that realization, our engineers built a rst-of-its-
kind independent wheel end coupler vacuum delete kit.
Designed to be replaced as a pair, this patent-pending
product looks and ts like the original, but simply
establishes a robust, permanent connection between
the two components. It also includes vacuum caps on
the hub, for holding the remnant vacuum lines, in case
the owner ever wants to revert to the original design in
the future.
“We have a lot of respect for OEMs. It’s just that
sometimes they make engineering tradeos for various
reasons, and the designs can be more trouble than
they’re worth,” said Steve Butcher, a Product Manager
in our Undercar unit. “This is a good example where we
were able to give vehicle owners more freedom to x
their vehicle however they choose.”
AFTERMARKET CASE STUDY
4WD HUB LOCKING ACTUATOR DELETE
OE Problem:
The original wheel end actuator on
certain vehicles is highly failure prone,
leading to a loss of vacuum, and an
inoperable 4WD system.
FIX
We found that the hub locking actuator
created signicant problems without
adding much value for many owners.
This patent-pending vacuum delete
kit restores critical operation, while
eliminating failure-prone features,
and adding increased durability and
serviceability.
Grease Fittings
allows end user
to easily lubricate
the gear
Staked Plugs
allow for original vehicle
vacuum lines to connect
without the need to cut
or splice hoses
