17NA281

File in Section:
Bulletin No.:
Service Bulletin
Date:
17-NA-281
September, 2017
INFORMATION
Subject:
RDM Axle Ratios for AWD Vehicles for Vibration Diagnostics When Using the Pico
Scope
Brand:
Model:
Buick
Model Year:
VIN:
from
Rear Axle Ratio
from
to
to
LaCrosse
Regal
2010
2018
2.769:1
Buick
Envision
2017
2018
2.769:1
Buick
Enclave
2008
2018
2.733:1
Buick
Encore
2014
2018
2.529:1
Cadillac
SRX
2010
2016
2.769:1
Cadillac
XTS
2010
2018
2.769:1
Cadillac
XT5
2017
2018
2.769:1
Chevrolet
Equinox
Captiva
2010
2017
2.533:1
Chevrolet
Equinox
2018
2018
2.769:1
Chevrolet
Traverse
2009
2018
2.733:1
Chevrolet
Trax
2014
2018
2.529:1
GMC
Terrain
2010
2017
2.533:1
GMC
Terrain
2018
2018
2.769:1
GMC
Acadia (VIN
R or V)
2007
2018
2.733:1
GMC
Acadia
(VIN N)
2017
2018
2.769:1
Saturn
OUTLOOK
2007
2010
2.733:1
Saturn
VUE
2008
2009
2.533:1
Involved Region or Country
North America
Condition
During diagnosis of a vibration concern on AWD vehicles with transaxles, it is important
to note that the rear axle ratio is not the same as the RPO final drive ratio shown in the
Vehicle Build section of Global Warranty Management.
Cause
The RPO final drive ratio is the final drive ratio in the transmission and not the same as
the rear axle (RDM) ratio. The rear drive axle on AWD vehicles is driven by a transfer
case (referred to as a PTU or Power Take-Off Unit) through a longitudinal propeller shaft.
The PTU speeds up and reduces the torque to the propshaft then the RDM slows down
and increases the torque to the wheels. Because the torque is reduced, we can use a
smaller, lighter propshaft. The smaller propeller shaft fits in a tighter space as well as
transmits less energy to the vehicle while in operation, reducing noise and vibration.
Correction
The correct RDM final drive ratio to use for vibration diagnostics can be found in the
Driveline/Axle, Rear Drive Axle, Specifications page in SI.
Copyright 2017 General Motors LLC. All Rights Reserved.
Page 2
September, 2017
Bulletin No.: 17-NA-281
Parts Information
No parts are needed for this concern.
Version
1
Modified
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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