GMC T Series 1994 Repair Manual page 838

MODEL 233
The Model 233 is an electronic shift transfer case
with three modes of operation: two-wheel drive range,
four-wheel drive high range and four-wheel drive low
range. Gear reduction for low range is provided by a
planetary gear set. The floor-mounted shifter has been
eliminated on vehicles equipped with this transfer case.
A switch located on the upper left side of the instrument
panel on the utility and upper right side of the pickup is
used to select the operating range. Indicator lamps on
the switch show the current mode of operation.
W hen four-w he el drive has been selected, the
four-w heel drive indicator lam p on the sw itch is
designed to come on when the front axle has engaged.
The lamp will blink while the front axle is engaging. This
is normal.
The 233 has a two-piece aluminum case containing
front and rear output shafts, two drive sprockets, an
electronic shift m echanism , and a planetary gear
assembly (figures 1 and 2). The drive sprockets are
A. INDENTIFICATION TAG
3. BOLT, EXTENSION HOUSING AND CASE HALF
4. HOUSING, EXTENSION
8
. HOUSING, PUMP RETAINER
15. PLUGS, DRAIN/FILL
17. CASE HALF, REAR
44. RETAINER, INPUT BEARING
45. CASE HALF, FRONT
46. SWITCH, VACUUM
74. YOKE, FRONT OUTPUT
77. NUT, FRONT OUTPUT YOKE
94. MOTOR, ENCODER
GENERAL DESCRIPTION
Figure 1—233 Rear Case Half
connected and operated by the drive chain. The plane­
tary gear assembly consists of a 4-pinion planetary car­
rier and an annulus gear that provide the four-wheel
drive low range when engaged. The reduction ratio is
2.72:1 in this range. The electronic shift mechanism is
controlled by an electronic shift encoder motor mounted
on the front half of the transfer case.
IDENTIFICATION
An identification tag is attached to the rear half of the
transfer case (figure 1). This tag provides the transfer
case model number, low range gear reduction ratio, and
assembly number. The information on this tag is neces­
sary when servicing this transfer case. If the tag is
removed or becomes dislodged during service opera­
tions, be sure to keep the tag with the unit.
POWER FLOW
In all drive range positions input torque is transmitted
to the transfer case gear train through the transfer case
input gear. In 2HI range, torque flows from the input
V2924
V2923