Operating Ranges - Hummer H1 Service Manual

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OPERATING RANGES

The three operating ranges are for specific use on or off road.
Usage recommendations are:
High Lock (HL)
High lock range is for use on low traction surfaces. It is an un-
differentiated range and should only be employed on unpaved,
or low traction surfaces; low traction defined as surfaces cov-
ered by snow, ice, sand, mud, or dirt. The differential is by-
passed (locked out) in this range.
High (H)
High range is the only range recommended for use on hard, or
paved road surfaces. This range can be used on, or off-road as
desired.
Low (L)
Low range is for low speed, off road operation. The extra pull-
ing power provided is useful when traversing steep grades, or
driving in deep mud or sand. The low range gear provides a
2.72:1 reduction ratio when locked in the low range annulus
gear.
Neutral
Neutral range is used for towing purposes.
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Transmission/Transfer Case
TRANSFER CASE SHIFTING
The transfer case shift lever is adjacent to the transmission shift
lever. A straight-line shift pattern is employed (Figure 5-69).
The transfer case can be shifted from High (H) to High Lock
(HL) and back, at any legal speed without putting the transmis-
sion in neutral.
The vehicle must be completely stopped and the transmission
shifted to neutral before a shift to low range (L). This is neces-
sary because the low range gear must be moved into engage-
ment with the fixed annulus. Once the low range and annulus
are engaged, the transfer case is locked into a 2.72:1 reduction
ratio. All output to the propeller shafts is undifferentiated and
equal. Maximum recommended vehicle speed in low range is
23-31 mph (37-50 kph), with the lower speed preferred.
TRANSFER CASE
OPERATING
RANGES
Figure 5-69: Transfer Case Shift Lever and Bezel
TRANSFER CASE DIAGNOSIS
The diagnosis guides outline probable causes of various trans-
fer case malfunctions. The problem causes are listed in order of
potential (most to least probable). The guides do not cover ev-
ery possible condition or possibility. They do however, provide
a means of reducing the number of components requiring fur-
ther diagnosis and inspection.
5-151