Chevrolet 10 Series 1970 Service Manual page 474

CLUTCHES AND TRANSMISSIONS 7-44
A pproxim ate Altitude
of Check (F t. Above
Sea L e v e l)
2000
4000
6000
8000
10000
12000
14000
F ig . 6 —V acuum M o d u la to r Assem bly
V A C U U M M ODULATOR ASSEMBLY
1. Vacuum D iaphragm Leak Check
In sert a pipe clea n er into the vacuum connector pipe
as fa r as p ossible and check fo r the p resence of tra n s­
m ission oil. If o il is found,
NOTE: G asoline or w ater vapor may settle in
the vacuum side of the modulator.
found without the p resen ce of oil, the modulator
should not be changed.
2. Atmospheric Leak Check
A pply a lib e ra l coating of soap bubble solution to the
vacuum connector pipe seam , the crim ped upper to low er
housing seam (F ig . 6).
tubing, apply a ir p ressu re to the vacuum pipe by blowing
into the tube and observe fo r leak bubbles. If bubbles
appear, rep lace the m odulator.
NOTE: Do not use any method other than human
lung pow er fo r applying a ir pressu re, as p r e s ­
sures ov e r 6 psi m ay damage the modulator.
Absolute
M anifold
P re ss u re
("H g)
0 16
16
16
16
16
16
16
16
rep lace the modulator.
If this is
Using a short p iece of rubber
R ela tive
D rive
Engine
N eutral
Vacuum
P a rk
("H g)
13.92 76
11.83 79
9.86 82
7.96 85
6.23 87
4.58 90
3.04 92
1.59 94
ENDS TO BE SQUARE
SCRIBED LINE
F ig . 7 —B ellow s C om parison G au ge
3. Bellows Comparison Check
Using a com parison gauge, as shown in F ig. 7, com ­
p are the load of a know good Turbo H yd ra -M a tic 350 mod­
u lator with the assem bly in question.
A. In stall the modulator that is known to be acceptable
on eith er end of the gauge
B. In stall the modulator in question on the opposite end
of the gauge.
C. Holding the m odulators
bring them together
m odulator sleeve end just touches the line in the
center of the gauge. The gap between the opposite
m odulator slee ve end and the gauge line should then
be 1/16" or le ss.
this amount, the modulator in question should be
replaced.
4. Sleeve A lignm ent Check
R o ll the main body of the m odulator on a fla t surface
and observe the s le ev e fo r con cen tricity to the cam. If
the sle eve is concentric and the plunger is fre e , the mod­
u lator is acceptable.
Once the m odulator assem bly passes a ll of the above
tests, it is an acceptable part and should be re-used.
L -6 and
V-8 R e v erse
L I or L2
94 120
96 124
98 129
133
100
102 137
103 141
105 144
107 148
1 3 / 3 2 " TO 3 / 8 "
R O U N D OR FLAT STOCK
in a horizon tal position,
under p ressu re until eith er
If the distance is g re a te r than
CHEVROLET TRUCK SERVICE MANUAL