Hummer 2006 H3 Owner's Manual page 217

Design specifications required a minimum gradeability of
60% (31 degrees) slope, with the vehicle fully loaded,
on high friction surfaces with maximum vehicle
speed not to exceed 6 mph (9.7 km/h). The vehicle
is expected to traverse this grade only for short
durations. Never stop and idle the vehicle or park
it on this grade.
Also, your vehicle should be able to traverse a
40% (22 degrees) side slope at 6 mph (9.7 km/h)
while fully loaded on high friction surfaces.
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