Chevrolet 70 Series 1970, Service Manual

Page: 635 / 841

TRANSMISSIONS AND CLUTCHES 7-36
The sh ift p iston is moved by rem oving or ap­
plying a ir (from constant supply) to the b a ck -sid e
of p iston . T his p isto n a r e a i s la rg er and can o v e r ­
com e area of front sid e of piston. The rem oval or
application of air on backside of p iston i s co n tro ll­
ed by the in se r t valve in cylinder cover; th is valve
in turn i s con trolled by the sp litter control v a lv e.
INSERT VALVE (R efer to F ig. 18)
The in se r t valve located in the sh ift cylinder
c o v e r i s a sm a ll 1 -3 /1 6 " Humphrey v a lv e. It is
in sta lle d with the flat su rfa ce to the in sid e towards
the cen ter port, and it is secu red with a sp e c ia l
nut in bottom bore of cover.
When in stallin g in sert valve apply Dow Corning
#200 Lubricant or its equivalent to cylinder w a lls.
When in stallin g sp e c ia l nut apply L octite hydraulic
sea la n t to threads.
The in se r t valve is self-co n ta in ed and cannot
b e d isa sse m b le d except fo r the th ree O -rin g s on
outer d iam eter. T h ese three O -rin g s a re a station ­
ary s e a l and do not m ove in cylin d er.
T ravel of the sm a ll p iston in in se r t valve is
only 3 /1 6 " . The in se r t valve i s a norm ally-open
v a lv e. Thus, when th ere is no sign al or d elivery of
a ir to topside of in se r t piston, the constant air
from regulator p a s s e s through the in se r t valve and
to the b ack sid e of the piston and m oves the shift
bar forw ard ("DIRECT").
When the in se r t valve p iston i s activated by a
sign al o r d eliv ery of a ir , the in se r t valve is c lo se d
and shuts o ff the constant a ir to backside of shift
p iston . A ir in shift cylinder is exhausted out through
in se r t valve and bottom bore of co v er.
When a ir i s rem oved from backside of shift
p iston , constant a ir on front sid e of shift piston
m oves the sh ift bar to the rea r ("OVERDRIVE").
AUXILIARY TRANSMISSIONS
(SPICER MODELS 6041, 7041, 8341F, AND 8345F)
T his sec tio n c o v e rs o n -v e h ic le s e r v ic e in for­
m ation on S p icer A uxiliary T r a n sm issio n s. G ear
shifting is accom p lish ed by u se of the sh ift le v e r
in the cab, which is interconnected to the auxiliary
tr a n sm issio n with ca b le s or rods. The auxiliary
tr a n sm issio n is supported at the front by a sup­
port bracket attached to fram e sid e r a ils and at
the rear by a support beam attached to fram e
b ra ck ets. Hand brake (when used) and speedom eter
d rive a re at rear of tra n sm issio n .
LINKAGE ADJUSTMENT
ROD TYPE LINKAGE ADJUSTMENT
(R efer to F ig. 1)
1. D iscon n ect control rods from sh ift control
tow er under cab.
2. P la c e the auxiliary tr a n sm issio n gearsh ift
le v e r and sh ift rods on the tr a n sm issio n in "NEU­
TRAL."
Figure 1 —Rod Type Auxiliary Transmission Linkage
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL