Chevrolet 1980 Light Duty Truck Service Manual page 183

of this manual should be used by owners, dealers and
repairmen as guidelines in vehicle diagnosis either for
repairs under the new vehicle warranty or for maintenance
service at customer's request. These specifications provide
an acceptable all-around operating range in that they
prevent abnormal tire wear caused by wheel alignment.
Governmental Periodic Motor Vehicle Inspection
programs usually include wheel alignment among items that
are inspected. To provide useful information for such
inspections, the specifications stated in column 2 of the
wheel alignment chart are given and these are well within
the range of safe vehicle operation.
In the event the actual settings are beyond the
specifications set forth in column 1 or 2 (whichever is
applicable), or whenever for other reasons the alignment is
being reset, the specifications given in column 3 of the wheel
alignment chart should be used.
It is good practice to set front end alignment to
specifications while the vehicle is in its
condition. Trucks which are
w ith heavy loads should have toe-in adjusted w ith
the truck under heavy load.
result in longer tire life.
A LIG N M E N T A D JU S TM E N TS
A normal shim pack will leave at least two (2) threads
of the bolt exposed beyond the nut. If two (2) threads cannot
be obtained, check for damaged control arms and related
parts. The difference between front and rear shim packs
must not exceed 7.62mm (.30 inches). Front shim pack must
be at least 2.54mm (.10 inches).
Access to Shim Packs
G 10-20 Models, C IO Models w ith 3 /4 " Nut:
With vehicle on front end rack, jack at frame and raise
the wheel off the ground. This will allow the upper control
arm to pivot down far enough to use a socket on the nuts
and permit shim removal.
PIVOT SHAFT OUTBOARD OF FRAME
CASTER
Fig. 3 A -2 -C a ste r - Cam ber A d ju s tm e n t
normally loaded
consistently operated
This procedure should
A
CAMBER
FORWARD
G 30 Models, C 2 0 and 30 Models w ith 7 /8 "
Nut:
Remove the upper control arm bumper; then follow the
same procedure as above. Reinstall the upper control arm
bumper when alignment is completed.
Caster
All caster specifications are given assuming a frame
angle of zero. Therefore, it will be necessary to know the
angle of the frame (whether "up" in rear or "down" in rear)
before a corrected caster reading can be determined.
Camber and toe can be read "as is" from the alignment
equipment.
How to Determine Caster (Fig. 3A-4)
All caster specifications are given assuming vehicle
frame angle is zero. Therefore, it is necessary to adjust
specifications when applying them to vehicles with any
frame angle other than zero.
1. With vehicle on a level surface, determine frame
angle (whether up or down in rear) with the use of a bubble
protractor or inclinometer. Record this measurement (See
Figure 4).
2. Measure dimension "A" (See Figure 4).
3. Check and record specifications for caster under
that column related to dimension "A" as measured in step
2
.
4. Using one of the following rules, add or subtract
frame angle found in step 1 to or from specification found
in step 3.
a. A down-in-rear frame angle must be added to a
positive caster specification.
b. An up-in-rear frame angle must be subtracted from
a positive caster specification.
c. A down-in-rear frame angle must be subtracted from
a negative caster specification.
d. An up-in-rear frame angle must be added to a
negative caster specification.
FRONT A LIG N M E N T
LIG H T T R U C K S ER V IC E M ANUAL
3A-3