Lunchbox Locker -
Automatic Lockers
Lockers, Limited Slips, Differentials
and the sport
of Offroading.
An Overview of Standard Carriers, Positraction & Limited
Slips,
Locking Differentials, Spools and Mini-Spools |
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Lunchbox Locker - A "Lunchbox" locker (or drop-in
locker) is a locker mechanism that is designed to fit into the stock
differential carrier replacing the spider gear set and sometimes the side
gears and pinion-shaft. The nickname "Lunchbox" comes from the idea
of packing your lunch in a reusable "lunchbox" where you use the same
"lunchbox" and pack in a different lunch. The stock carrier is the
equivalent of the "lunchbox".
 Lunchbox
lockers come with advantages and disadvantages. An advantage that
comes with these drop-in lockers are the fact that they are generally
simple devices and are designed to fit into a stock open carrier or in
some cases limited slip carrier, reusing stock parts. Since the ring
gear is connected to the carrier and the carrier is reused, the ring and
pinion gears generally do not need to be setup again. This makes it
much easier for a backyard mechanic to install a drop-in "lunchbox"
locker. It also allows the locker to be removed and the stock
carrier parts be re-installed putting it back to an open carrier (or
Limited Slip). Disadvantages of these types of lockers include the
fact that their strength is limited to the carrier they are installed in,
which can vary greatly. Their strength is moderate to less than
moderate and for the most part support what seems to be up to a 33" tires
and a mild amount of abuse before encountering problems and damage.
Another disadvantage to a drop-in locker is that some have a more severe
locking and unlocking feel over a full carrier locker. For this
reason some drop-in locker manufacturers incorporate dampening mechanisms
to reduce the backlash and harsh engagement / disengagement creating a
smoother operating locker. For many people they are a good candidate
for a first "economy" locker on vehicles that are mildly modified with
slightly oversized tires.
 Lunchbox
Lockers operate in much the same manner as full carrier automatic lockers.
These locker are automatic locking differentials
designed to lock both wheels of the axle automatically with power input, when
forward or reverse torque is
applied, so that both wheels are providing 100% power to the wheels and
creating essentially a "spool" that solidly connects the axle shafts
together. When torque is not
being applied, the locker is
allowed to unlock, permitting a differentiation
variance in wheel speed while negotiating turns. As an automatic
locking differential, the primary drawback is their characteristics when
they engage such as accelerating out of a turn or going from torque to no
to torque to torque again such as when a manual transmission vehicle is
shifting gears. In these situations, the driver must be aware of the
characteristics that will affect the handling of the vehicle. For
example during a turn the inside axle will spin slower than the outside
axle, which is the basic purpose of the differential. If torque is
applied to an automatic locker during the turn it will engage due to the
torque engaging the locker gears. When the
locker engages, it will cause the vehicle to push towards straight ahead
or possibly to the inside of the turn. The net effect is somewhat
un-predicable handling characteristics when compared to open
differentials. These effects are much more
noticeable in shorter wheelbase vehicles and smaller lighter vehicles.
The odd handling characteristics will also be more apparent if road
traction is compromised such as in rain or when the road surface is ice
or snow covered. Further noticeable characteristics of automatic
lockers can be a banging or clunking noise during engagement of
disengagement, delayed engagement, and added significant backlash, also
known as slop, in the driveline. Disengagement can be abrupt and
sometimes a ratcheting noise can be heard when cornering. Most people who use
automatic lockers become
accustom to these handling characteristics and adjust their driving
style accordingly to accommodate it or just simply just get used to it.
Some Lunchbox Lockers on the market are:
Lockright Locker by Richmond Gear
Detroit
EZ Locker made by Eaton Corporation
Aussie Locker by Torq-Masters Technology, Inc.
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