Chevrolet 10 Series 1970 Service Manual page 223

POWER SOURCE
(IGNITION OR
ACCESSORY SWITCH)
I
8
CIRCUIT
BREAKER
\
M
in harness may be broken.
harness may also be faulty.
Solenoid V a lv e Check
The solenoid va lv e is e n ergized to supply a ir to shift
the unit into high axle range only. The va lve must have a
good ground connection to veh icle in o rd e r to operate
s a tis fa c to rily . Make certain that ground connection is
sa tis fa c to ry b efo re checking valve.
D isconnect lead w ire at C and disconnect a ir line lead ­
ing to shift unit. Install a ir p ressu re gauge in a ir line
opening in solenoid v a lv e . Apply voltage to solenoid valve
term in a l and o b serve p ressu re gauge reading.
If gauge indication is approxim ately that of r e s e r v o ir
p ressu re, solenoid va lve is sa tisfa ctory . If gauge in dica­
tion is low o r no p re s s u re ,
Piston A ir-Shift Unit Check
If e le c tric a l system is s a tisfa ctory and axle does not
sh ift p ro p e rly , trouble m ay be caused by a faulty shift
unit. D isassem ble and r e p a ir unit as outlined in this
Manual.
Speedom eter A d ap ter Check
The speedom eter adapter is e n ergized in low axle
range only. The adapter is grounded through speedom ­
e te r mounting o r speedom eter cable and cable housing.
Make certain that p rop er ground is presen t b e fo re check­
ing adapter.
Disconnect lead w ire at B and connect test lamp to
lead B and veh icle ground.
o b serve test lamp.
The test lamp should ligh t in low range position of
SWITCH
CONTROL
SWITCH
SOLENOID
SPEEDOMETER
ADAPTER
WIRING
HARNESS
F ig . 81 — Piston A ir S h ift System
Plug assem bly in w irin g
solenoid va lve is faulty.
Turn ignition switch on and
SINGLE
DRIVE AXLE
CONNECTION
FROM AIR
RESERVOIR
con trol switch. Lam p should go out when con trol switch
is in high range position.
If lamp indications
adapter is c o rre c t.
axle shifts p ro p erly , but speedom eter does not operate
p ro p erly , replace adapter.
If test lamp indications a re not c o rre c t, trouble is in
w irin g harness o r con trol switch.
Piston A ir-Shift Unit
A Piston A ir-S h ift Unit is used with the 23,000 lb.
Eaton Tw o-Speed A x les , see
operated when a supply of a ir is released into the c y l­
inder. The piston tra v e ls downward against a c o m p res­
sion spring, tra n s ferrin g motion through the push rod and
actuating le v e r to the shift fork, shifting the axle into
" H i " ratio. Exhaust o f a ir pressu re fro m the cylin der
p erm its the piston and spring to return the axle gearin g
to " L o " ratio.
Removal
1. Bleed a ir fro m shift unit cylin der and disconnect a ir
line at piston housing cover.
2. Rem ove two stud nuts retaining shifting unit and pull
unit fro m d ifferen tia l c a r r ie r .
3. Rem ove shift fo rk seal and spring.
Disassembly
1. R em ove bolts,
gasket fro m shift
2. Position housing in v is e
3. Rem ove nuts and bolts retaining piston housing c o v e r
to unit. Rem ove piston housing c o v e r and " O " ring
sea l, replace seal
REAR SUSPENSION AND DRIVE LINE 4-47
PISTO N A IR -SH A FT UNIT
a re c o rrec t, cu rren t supply to
If lamp indications a re c o r r e c t and
Figu re 82. This unit is
lock w ashers, housing c o v e r and
unit housing. Drain lubricant.
as shown in F igu re
w henever co v e r is
CHEVROLET TRUCK SERVICE MANUAL
83.
rem oved.