Speedometer Adapter Shift Diaphragm; D E Sc Rip Tio; Air Shift System Troubleshooting - Chevrolet 40 SERIES 1971 Service Manual

SPEEDOMETER ADAPTER
SHIFT DIAPHRAGM
When sh ift co n tro l le v e r is m oved to "HI"
p o sitio n , cavity behind sp e e d o m e te r a d a p te r sh ift
d iap h rag m (fig. 27) is su b je c te d to a tm o sp h e re
th ro u g h the sh ift c o n tro l valve. S pring m ovem ent
of d iap h rag m is tra n s m itte d to the sp e e d o m e te r
a d a p te r le v e r by th e d iap h rag m ro d , shifting the
s p e e d o m e te r a d a p te r g e a rs into high ra tio . When
th e c o n tro l le v e r is m oved to "L O " p o sitio n , the
c o n tro l v alve a d m its vacuum to the cavity behind
th e d iap h rag m and fo rc e s d ia p h ra g m and ro d in ­
w a rd , sh iftin g the sp e e d o m e te r a d a p te r g e a rs into
low ra tio .
REMOVAL AND DISASSEMBLY
1. D isco n n ect vacuum
d iap h ra g m body.
2. R em ove two s c r e w s attach in g diap h rag m
b ra c k e t to sp e e d o m e te r a d a p te r. L ift diap h rag m
and b ra c k e t to unhook d iap h rag m ro d fro m a d a p te r
le v e r and rem o v e d iap h rag m and b ra c k e t a sse m b ly .
3. R em ove fo u r s c re w s attach in g body to b r a c ­
k e t. R em ove body, sp rin g and d iap h rag m and ro d
a sse m b ly fro m b ra c k e t.
INSPECTION
1. E xam ine d ia p h ra g m fo r c ra c k s o r o th e r
d am ag e. R ep lace a sse m b ly if diap h rag m is d a m a g e d .
2. C heck condition and te n sio n of diap h rag m
s p rin g . If s p rin g is c o rro d e d o r if te n sio n is not
su ffic ie n t to r e tu r n d ia p h ra g m to r e le a s e p o sitio n ,
re p la c e a sse m b ly .
ASSEMBLY AND INSTALLATION
1. P o sitio n th e d iap h rag m and ro d a sse m b ly ,
DESCRIPTION
An a i r sh ift c o n tro l is u se d optionally in con­
junctio n w ith th e E aton Model 19201 tw o -sp eed
a x le . S e rv ic e o p e ra tio n s and tro u b le shooting p r o ­
c e d u re s p e rta in in g to th is s y s te m a r e outlined
below:
AIR SHIFT SYSTEM
TROUBLESHOOTING
(R efer to F ig u re 28)
If ax le w ill not sh ift, te s t sy ste m and com pon­
e n ts a s follow s:
NOTE: T e s t lam p voltage m ust be sa m e a s
s y s te m r a te d v o ltage.
lin e fro m the sh ift
TWO-SPEED AXLE AIR SHIFT SYSTEM
REAR AXLE AND CONTROLS
s p rin g , and body on d iaph rag m b ra c k e t and a tta c h
w ith fo u r s c re w s . S crew s m ust be tig h te n ed s u f­
ficien tly to m ake the a sse m b ly a ir - tig h t w ith two
pounds of a i r p r e s s u r e .
2. P o sitio n d iap h rag m and b ra c k e t a sse m b ly
a t sp e e d o m e te r a d a p te r, hooking d iap h rag m ro d
into a d a p te r le v e r . A ttach d iaphragm b ra c k e t to
a d a p te r w ith two s c re w s and w a s h e rs .
3. C onnect vacuum lin e to d iap h rag m body.
T ighten connection firm ly .
CIRCUIT BREAKER CHECK
D isco n n ect c irc u it b re a k e r lea d w ire a t te r m ­
in al (A) and connect te s t lam p fro m te rm in a l (A)
to ground. T u rn on ignitio n sw itch and o b se rv e te s t
lam p .
1. If lam o lig h ts and sta y s on, c ir c u it b re a k e r
and le a d w ire a r e s a tis fa c to ry .
2. If lam p does not light, check fo r p o o r e le c ­
t r ic a l connections o r b ro k en lead w ire . If le a d w ire
and co nnections a r e sa tis fa c to ry , c irc u it b re a k e r
is fau lty .
3. If lam p does not lig h t im m e d iate ly but then
s t a r t s to fla sh (also a fa in t click in g of the c irc u it
b r e a k e r may be h e a rd ), th e c irc u it b re a k e r is
fau lty .
Sec. 4A-19
CHEVROLET 40-60 TRUCK SERVICE MANUAL