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21 - 36
MANUAL TRANSMISSION
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NP435 MANUAL TRANSMISSION
INDEX
Page
Component Assembly
38
Component Disassembly
38
General Information
36
Service Diagnosis .
36
Page
Transmission Assembly . . . . . . . . . . . . . . . . . . . . .
41
Transmission Disassembly
37
Transmission Installation . . . . . . . . . . . . . . . . . . . .
42
Transmission Removal
.
37
GENERAL INFORMATION
The NP435, four-speed m a n u a l transmission used
for heavy service applications (Fig. 1). Second, t h i r d ,
and f o u r t h gears are helical, constant mesh gears
w i t h synchronizers. F i r s t and reverse gears are spur
type a n d n o t synchronized. The reverse idler gear is
serviced as a n assembly complete w i t h i n t e g r a l bear-
ings. T h e countershaft gear is a one-piece design.
A b a l l b e a r i n g supports t h e m a i n drive p i n i o n . A
pilot r o l l e r bearing recessed i n the m a i n drive p i n i o n
supports t h e f r o n t end of themainshaft w i t h t h e rear
end supported by a b a l l bearing.
The f r o n t synchronizer u n i t consists of a s l i d i n g
clutch gear, energizer springs, floating solid pins and
synchronizer cones. The u n i t is serviced only as a n
assembly. T h e stop rings can be serviced
separately
but should be used i n sets w i t h the new floating solid
pin type synchronizer.
J902M55
Fig. 1 NP435 Manual Transmission
SERVICE DIAGNOSIS
The
m a j o r i t y
of transmission malfunctions are
caused by insufficient lubricant, incorrect l u b r i c a n t ,
misadjusted or damaged i n t e r n a l components, loose
a t t a c h i n g parts, or improper operation.
HARD
SHIFTING
A l o w l u b r i c a n t level, loose or w o r n shift lever, or
loose, damaged shift housing components are com-
m o n causes of h a r d s h i f t i n g . I f h a r d s h i f t i n g is also
accompanied by gear clash, synchronizer stop r i n g s
or mainshaft clutch gear t e e t h m a y be w o r n or dam-
aged.
H a r d s h i f t i n g m a y also be caused b y a loose, or
misaligned shift housing. E i t h e r f a u l t can r e s u l t i n
component bind and h i g h shift efforts.
NOISY
OPERATION
Transmission noise is most often a r e s u l t o f w o r n
or damaged components.
Chipped, b r o k e n gear or
synchronizer teeth a n d b r i n n e l l e d , spalled
bearings
a l l cause noise. A b n o r m a l wear and damage t o i n t e r -
n a l components i s frequently t h e end result o f insuf-
ficient
lubricant,
non-recommended
l u b r i c a n t s , or
improper operation.
SLIPS
OUT OF GEAR
Transmission disengagement m a y be caused b y
misaligned or damaged shift components, or w o r n
synchronizer clutch teeth on t h e mainshaft gears. I n -
correct assembly w i l l also contribute t o gear disen-
gagement.
LOW LUBRICANT
LEVEL
Insufficient transmission l u b r i c a n t is u s u a l l y t h e
result of leaks, or inaccurate fluid level check or re-
f i l l method. Leaks w i l l be evident by t h e presence of
gear o i l around t h e leak point. I f leakage is n o t evi-
dent, t h e condition is probably t h e r e s u l t o f a n u n -
d e r f i l l condition.
I f a i r powered l u b r i c a t i o n equipment is used to fill
a transmission, be sure t h e equipment is properly
calibrated. Equipment o u t o f c a l i b r a t i o n can lead to
an u n d e r f i l l condition.
CLUTCH
PROBLEMS
W o r n , damaged, or misaligned c l u t c h components
can cause difficult shifting, gear clash and noise.
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