Gaging Procedure - GMC 1990 Light Truck Repair Manual

1B1-14 A-6 AIR CONDITIONING COMPRESSOR
Figure 32—Gaging the Rear Piston Bail

GAGING PROCEDURE

Tools Required:
J 8001 Dial Indicator Set
J 9397 Compressing Fixture
J 9402 Piston Assembly Tray
J 9661 -01 Feeler Tension Gage Set
Two gaging procedures provide the running toler­
ances.
The first procedure determines the size shoe discs to
provide at each piston a 0.041-0.061 mm (0.0016-
0.0024-inch) total preload between the seats and the
axial plate at the tightest place through the 360 degree
rotation of the axial plate. The bronze shoe discs are
available in 0.013 mm (0.0005-inch) variations.
The second procedure, performed at the rear shaft
thrust bearing and race pack, provides a 0.064-0.077
mm (0.0025-0.0030-inch) preload between the hub sur­
faces of the axial plate, and the front and rear hubs of
the cylinder. Fourteen steel thrust races, including a
basic "zero" race, are available in 0.013 mm (0.0005-
inch) increments. Use J 9661 -01 for gaging the shoe
disc size. Use J 8001 to determine the thrust race size.
1. Measure the clearance between the rear ball of
the No. 1 piston and axial plate in the following
manner:
a. Select a combination of oiled feeler gage
leaves to fit snugly between the ball and axial
plate.
b. Attach J 9661 -01 to the feeler gage. A distribu­
tor point checking scale may be used.
c. Pull on the spring scale to slide the feeler gage
stock out from between the ball and axial
plate. Note the reading on spring scale as the
feeler gage is sliding out (figure 32). The read­
ing should be between 1.1 and 2.2 N (4 and 8
ounces).
d. If the reading in step c above is under 1.1 N (4
ounces) or over 2.2 N (8 ounces), reduce or
increase the thickness of the feeler gage
leaves and repeat steps a through c to obtain
a reading of 1.1 N to 2.2 N (4 to 8 ounces).
Record the clearance between the ball and axi­
al plate that results in the 1.1 N to 2.2 N (4 to
8 ounces) pull on the spring scale.
2. Rotate the shaft 120 degrees and repeat for the
No. 2 cylinder.
• If the shaft is hard to rotate, install the shaft
nut onto the shaft and turn the shaft with a
wrench.
3. Rotate the shaft another 120 degrees and repeat
for cylinder No. 3.
4. Select a numbered shoe disc corresponding to the
minimum feeler gage reading recorded in the
three checks:
• Place the shoe discs in J 9402 compartment
with the discs corresponding to piston No. 1
and the rear ball pocket position.
• Shoe discs are available in 0.013 mm (0.0005-
inch) variations. Eleven sizes are available for
F1599
field servicing. Shoe discs are marked with the
shoe size which corresponds to the last three
digits of the part number (figure 33).