GMC 2009 Yukon XL Owner's Manual page 365

CAUTION:
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On some vehicles that have certain front mounted
equipment, such as a snow plow, it may be
possible to load the front axle to the front gross
axle weight rating (GAWR) but not have enough
weight on the rear axle to have proper braking
performance. If your brakes can not work properly,
you could have a crash. To help your brakes work
properly when a snow plow is installed, always
follow the snow plow manufacturer or installer's
recommendation for rear ballast to ensure a
proper front and rear weight distribution ratio, even
though the actual front weight may be less than
the front GAWR, and the total vehicle weight is
less than the gross vehicle weight rating (GVWR).
Maintaining a proper front and rear weight
distribution ratio is necessary to provide proper
braking performance.
Total vehicle reserve capacity is the difference between
your GVWR and the weight of your vehicle with full fuel
and passengers. It is the amount of weight you can add to
your vehicle before reaching your GVWR. Keep in mind
that reserve capacity numbers are intended as a guide
when selecting the amount of equipment or cargo your
vehicle can carry. If you are unsure of your vehicle's front,
rear, or total weight, go to a weigh station and weigh your
vehicle. Your dealer/retailer can also help you with this.
The total vehicle reserve capacity for your vehicle can
be found in the lower right corner of the Certification/Tire
label as shown previously.
See your dealer/retailer for additional advice and
information about using a snow plow on your vehicle.
Also, see Loading the Vehicle on page 4-33.
Emergency Roof Lamp Provisions
Vehicles with the RPO VYU snow plow prep package
also have an emergency roof lamp provision package,
RPO TRW. Wiring for the emergency roof lamp is
provided above the overhead console. See Auxiliary
Roof-Mounted Lamp on page 3-18 for switch location.
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