File in Section:
Bulletin No.:

Service Bulletin

Date:

04 - Driveline/Axle
14-04-20-001
May, 2014

INFORMATION
Subject:

Moan from Rear Differential During Low Speed Tight Turn Maneuvers

Models:

2014 Chevrolet Z/28 Camaro

Some customers may comment on a moan coming
from the rear end during low speed tight turn
maneuvers.
The 2014 Chevrolet Z/28 Camaro was designed to be
the ultimate track-capable Camaro and has features
and equipment that are not shared with other Camaros.
As an example, power is distributed to the rear wheels
via a limited-slip differential featuring a helical gear set,
rather than traditional clutch packs. The new design
enables the driver to apply more power and get through
corners faster, by continuously adjusting the torque
bias to maximize available traction.
The differential works in unison with Chevrolet’s
proprietary Performance Traction Management system,
which allows drivers to adjust the level of throttle and
brake intervention to match their capability and driving
environment.
Adding Friction Modifier to the Rear Differential to
Reduce the Moan
If the customer desires to reduce the moan, this can be
accomplished with the addition of a friction modifier to
the rear differential lube. The customer should be
advised that adding the friction modifier will reduce the
torque delivery during aggressive cornering.
To add the friction modifier, perform the following
actions:
1. Raise and support the vehicle. Refer to Lifting and
Jacking the vehicle in SI.
2. Remove the rear differential fill plug. Refer to >
Differential Oil Replacement (218 mm - Z28) in SI.
Notice: Prior to adding the limited-slip axle
additive, the bottle MUST be shaken vigorously for
at least one minute to mix the additive thoroughly,
then immediately poured into the differential.

3. In the United States, add 2 oz of P/N #88900330
LIMITED SLIP AXLE LUBRICANT ADDITIVE to
the differential.
In Canada add 59 ml of P/N #992694 ADDITIVE, L/
SLIP AXLE LUBRICANT to the differential.
4. Test drive the vehicle and apply 3 full lock-to-lock
turns in 2nd gear with light throttle application in
order to determine if the moan is gone.
⇒ If the moan is still present, add an additional
2 oz (59 ml) and then reevaluate. It is not
recommended to add more than a total of 4 oz
(118 ml) to the base lubricant.
Removing Friction Modifier From the Rear
Differential
It is possible that after adding the friction modifier and
driving their vehicle, the customer may become
dissatisfied with the vehicle track performance.
⇒ If the driver wishes to return the performance to the
levels prior to the addition of the friction modifier
then perform the following actions:
1. Drain the rear differential fluid.
Notice: Initial noise may return after flush and fill.
2. Flush and fill the rear differential with the proper
fluid.

Parts Information
Part Number

Description

88900330

LIMITED SLIP AXLE LUBRICANT
ADDITIVE (U.S.)

992694

ADDITIVE, L/SLIP AXLE LUBRICANT
(Canada)

88900401

LUBRICANT - REAR DIFFERENTIAL
SAE 75W90 (U.S.)

89021678

LUBRICANT - REAR DIFFERENTIAL
SAE 75W90 (Canada)

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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