Chevrolet Light Duty Truck 1973 Service Manual page 212

3-38 FRONT SUSPENSION
FOUR WHEEL DRIVE (SERIES K10 AND K20)
General D escription.......................................................... 3-38
Front A xle.......................................................................... 3-38
Transfer Case..................................................................... 3-38
Adapter Assembly............................................................ 3-38
Free Wheeling Hubs....................................................... 3-38
Maintenance and Adjustments...................................... 3-39
Ball Joint Adjustm ent..................................................... 3-39
Wheel Bearing A djustm ent........................................... 3-48
Component Parts Replacem ent..................................... 340
Free Wheeling Hubs....................................................... 340
K-10 Series....................................................................... 340
K-20 Series....................................................................... 341
Front Axle Assembly...................................................... 343
Primary purpose of four wheel drive is to provide
additional tractive effort in off-the-road driving in order
to overcome such obstacles as sand, deep mud or snow,
hilly terrain with steep grades, etc.
With four wheels capable of driving, all the vehicle and
payload weight is utilized to give maximum tire traction.
The power unit is driven through a transmission and
consists of an adapter and a two-speed transfer case with
a steering and driving front axle. A single control lever is
used to shift the transfer case from direct drive to low
four wheel drive at a ratio of 1.94 to 1, thus eight
forward speeds and two in reverse are provided.
Some vehicles (utility with automatic transmission and
eight cylinder engines) are equipped with a new Full
Time 4 wheel drive transfer case see section 7 for further
information.
Front wheel drive may be engaged or disengaged at any
time without clutching when the transfer case is in direct
drive; however, in returning to 2 wheel drive from 4
wheel drive the accelerator may have to be varied as
steady pressure is applied on lever. This releases gear
tooth pressure during shifting.
A yoke and trunnion universal joint permits continuous
power flow to each front wheel, regardless of the turning
angle.
Provisions for Power Take-off have been incorporated in
the transfer case.
FRONT AXLE
The front axle is a hypoid gear axle unit equipped with
steering knuckles. Axle assembly number and production
date are stamped on left tube of assembly. Conventional
truck service brakes are provided on all 4-wheel drive
units.
INDEX
Removal.............................................................................. 343
Installation......................................................................... 343
Disassembly...................................................................... 343
Assembly............................................................................ 347
Special Tools......................................................................... 349
GENERAL DESCRIPTION
TRANSFER CASE
The transfer case is basically the devise which controls
the "high" and "low" gear ranges. The shifting into
"low" range also initiates four wheel driving action by
connecting thru the front and rear axles. Four wheel
drive is also possible in the 4-HI range. Utility vehicles
with automatic transmission and eight cylinder engines
are equipped with a new Full Time 4 wheel drive system.
Refer to Section 7 for service procedures.
ADAPTER ASSEMBLY
The adapter assembly is the means of making a
mechanical connection between the transmission and the
transfer case. Different adapters are used dependent
upon the transmission and transfer case with which the
vehicle is equipped. Refer to Section 7 for service
procedures.
FREE WHEELING HUBS (Fig. 51)
Free-wheeling hubs are available for the front wheels of
all four wheel drive vehicles except those equipped with
the new Full Time 4 wheel drive transfer case. The
purpose of these hubs is to reduce friction and wear by
disengaging the front axle shafts, differential and drive
line from the front axle shafts, differential and drive line
from the front wheels when the vehicle is operated under
conditions where front wheel drive is not needed.
The engagement and disengagement of free-wheeling
hubs is a manual operation which must be performed at
each front wheel. The transfer case control lever must be
in
hubs. Both hubs must be in the fully locked or fully
unlocked position. They must not be in the free-wheeling
position when low all wheel drive is used as the
additional torque output in this position can subject the
rear axle to severe strain and rear axle failure may
result.
Wheel H ub..................................................................... 343
Spindle.............................................................................. 344
Axle Joint......................................................................... 344
Ball Joint Service.......................................................... 346
Replacement of Knuckle Assembly....................... 347
Spindle Components.................................................... 348
Wheel Hub Components............................................ 348
Wheel Bearing Adjustment..................................... 348
-wheel drive position when locking or unlocking
2
LIGHT DUTY TRUCK SERVICE MANUAL