GMC 2011 Sierra Denali Owner's Manual page 449

First Engine Oil Change After
Every 40 000 km/25,000 Miles
Four wheel drive only: Transfer
case fluid change (extreme duty
service) for vehicles mainly
driven off road in four wheel
drive. Vehicles used for farming,
mining, forestry, Department of
Natural Resources (DNR), and
snow plowing occupations meet
this definition. Check vent hose
at transfer case for kinks and
proper installation. Check to be
sure vent hose is unobstructed,
clear, and free of debris. During
any maintenance, if a power
washer is used to clean mud
and dirt from the underbody,
care should be taken to not
directly spray the transfer case
output seals. High pressure
water can overcome the seals
and contaminate the transfer
case fluid. Contaminated fluid
will decrease the life of the
transfer case and should be
replaced.
First Engine Oil Change After
Every 80 000 km/50,000 Miles
Engine air cleaner filter
replacement. See Engine Air
Cleaner/Filter on page 10 14.
Automatic transmission fluid
change (severe service) for
vehicles mainly driven in heavy
city traffic in hot weather, in
hilly or mountainous terrain,
when frequently towing a
trailer, or used for taxi, police,
or delivery service. See
Automatic Transmission Fluid on
page 10 11.
Service and Maintenance
Transfer case fluid change
(severe service) for vehicles
mainly driven when frequently
towing a trailer, or used for taxi,
police, or delivery service.
Check vent hose at transfer
case for kinks and proper
installation. Check to be sure
vent hose is unobstructed, clear,
and free of debris. During any
maintenance, if a power washer
is used to clean mud and dirt
from the underbody, care should
be taken to not directly spray
the transfer case output seals.
High pressure water can
overcome the seals and
contaminate the transfer case
fluid. Contaminated fluid will
decrease the life of the transfer
case and should be replaced.
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