Chevrolet 1977 light duty truck, Руководство по обслуживанию

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Fig. 7A-8B--Vacuum M od u la to r Assembly
presence of oil, the m odulator is serviceable and should
not be changed.
A tm ospheric Leak Check
Apply a liberal coating o f soap bubble solution to
the vacuum connector pipe seam, the crim ped upper to
lower housing seam (Fig. 7A-8B). Using a short piece o f
ru b b e r tubing, apply air pressure to the vacuum pipe by
blowing into the tube and observe for leak bubbles. If
bubbles appear, replace the modulator.
N O T E : Do not use any m ethod other than h u m a n
lung power for applying air pressure, as pressures
over 6 psi m ay d a m a g e the modulator.
Spring Tension Com parison Check
Using tool J-24466, as shown in Figure 7A-9B.
c o m p are the load o f a known good modulator with the
assembly in question.
a. Install the m odulator that is known to be
acceptable on either end o f the tool.
b. Install the modulator in question on the
opposite end o f the tool.
c. Holding the modulators in a horizontal
position, bring them together under pressure until either
m odulator sleeve ju st touches the tool. The indicator in
the gage will show white if the m odulator is acceptable.
A non-conform ing m odulator will cause the indicator to
shift, thus showing blue. If white does not appear, the
m odulator in question should be replaced.
Sleeve A lig n m en t Check
Roll the m ain body o f the m odulator on a flat
surface and observe the sleeve for concentricity to the
cam. If the sleeve is concentric and the plunger is free,
the modulator is acceptable.
Once the m odulator assembly passes all o f the above
tests, it is an acceptable part and m ay be re-used.
T R A N S M IS S IO N CLUTCH PLATES
D IA G N O S IS
1. Lined Drive Plates.
a. Dry plates with compressed air and inspect
the lined surface for:
1. pitting and flaking
2. w ear
3.
glazing
4. cracking
5. charring
6. chips or metal particles im bedded in lining.
If a lined drive plate exhibits any o f the above
conditions, replacem ent is required. Do not
diagnose drive plates by color.
2. Steel Driven Plates
W ipe plates dry and check for heat discoloration. If
the surface is smooth and an even color sm ear is
indicated, the plate should be reused. If severe heat
spot discoloration or surface scuffing is indicated,
the plate must be replaced.
3. Clutch Release Springs
Evidence o f extreme heat or burning in the area o f
the clutch m ay have caused the springs to take a
heat set and would justify replacem ent o f the
springs.
CAUSES OF B U R N E D CLUTCH PLATES
1. F O R W A R D C L U T C H
a. Check ball in clutch housing d am aged, stuck
or missing.
b. Clutch piston cracked, seals d am aged or
missing.
c. Low line pressure.
d. P um p cover oil seal rings missing, broken or
undersize; ring groove oversize.
e. Case valve body face not flat or porosity
between channels.
2. IN T E R M E D IA T E C L U T C H
a. Interm ediate clutch piston seals dam ag ed or
missing.
J -2 4 4 6 6
H O LD M O D U L A T O R S IN A H O R IZ O N T A L P O S IT IO N , AS S H O W N ,
B R IN G T H E M SLO W LY TO G E TH E R U N D E R PRESSURE