Chevrolet 10 Series 1968, Руководство по обслуживанию

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CLUTCHES AND TRANSMISSIONS 7-50
1. Pressures indicated below are at 0 output speed with
the vacuum modulator tube disconnected and with
engine at
1200 rpm.
Approximate
Altitude of Check
(Ft. above seal level)
Drive
Neutral
Park
L I
or
L2 Reverse
0
150 150 244
2,000 150
150 233
4,000 145 150 222
6,000 138
150
212
8,000 132
150
203
10,000
126 150 194
12,000 121
150
186
14,000 116 150 178
2. Pressures indicated below are with the vacuum tube
connected for normal modulator operation, and with
sufficient engine speed to stabilize pump pressure
(approx. 600-800 rpm).
NOTE: Pressures are not significantly affected
by altitude or barometric pressure when the
vacuum tube is connected.
Drive, Neutral, Park L I or L2 Reverse
25 150 107
TURBO HYDRA-MATIC MODULATOR
ASSEMBLY DIAGNOSIS
After thorough investigation of field returned modulator
assemblies, it has been found that over 50% of the parts
returned as defective were good. For this reason, the
following procedure is recommended for checking Turbo
Hydra-Matic modulator assemblies in the field before
replacement is accomplished.
1. Vacuum Diaphragm Leak Check
Insert a pipe cleaner into the vacuum connector pipe
as far as possible and check for the presence of trans­
mission oil. If oil is found, replace the modulator.
NOTE:
Gasoline or water vapor may settle
in the vacuum side of the modulator. If this is
found without the presence of oil, the modulator
should not be changed.
2. Atmospheric Leak Check
Apply a liberal coating of soap bubble solution to the
vacuum connector pipe seam, the crimped upper to lower
housing seam, and the threaded screw seal (Fig. 5T).
Using a short piece of rubber tubing apply air pressure
to the vacuum pipe by blowing into the tube and observe
for leak bubbles.
If bubbles appear, replace the
modulator.
NOTE: Do not use any method other than human
lung power for applying air pressure, as pres­
sures over
6
psi may damage the modulator.
3. Bellows Comparison Check
Using a comparison gauge, as shown in Fig. 6 T, com­
pare the load of a known good Hydra-Matic modulator
with the assembly in question.
a. Install the modulator that is known to be acceptable
on either end of the gauge.
b. Install the modulator in question on the opposite end
of the gauge.
c. Holding the modulators in a horizontal position,
bring them together under pressure until either
modulator sleeve end just touches the line in the
center of the gauge. The gap between the opposite
modulator sleeve end and the gauge line should then
be 1/16" or less. If the distance is greater than
this amount, the modulator in question should be
replaced.
4. Sleeve Alignment Check
Roll the main body of the modulator on a flat surface
and observe the sleeve for concentricity to the can. If the
sleeve is concentric and the plunger is free, the modula­
tor is acceptable.
Once the modulator assembly passes all of the above
tests, it is an acceptable part and should be re-used.
CHEVROLET TRUCK SERVICE MANUAL