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AUTOMATIC TRANSMISSION
21 - 111
A-500/A-518 AUTOMATIC TRANSMISSION
INDEX
" Page
Page.
Cleaning and Inspection . . . . . . . . . . . . . . . . . . .
122
Overdrive Unit Installation
128
General Information •
111
Overdrive Unit Removal
116
Overdrive Geartrain Assembly and Adjustment
. . 124
Overdrive Unit Service Diagnosis
115
Overdrive Geartrain Disassembly
. 1 2 1
Overdrive Valve Body Service
116
Overdrive Unit Assembly and Adjustment
. . . . .
127
Service Diagnosis
113
Overdrive Unit Disassembly
. . . . . . . . . . . . . . . .
117
GENERAL INFORMATION
DESCRIPTION/APPLICATION
The A-500/518, four speed automatic transmissions
are a unique two-section design. They consist o f a
modified Chrysler three speed automatic t r a n s m i s -
sion w i t h a n overdrive u n i t attached to t h e rear o f
the transmission (Fig. 1).
TRANSMISSION
Fig. 1 A-500/518 Transmission And Overdrive Unit
The f r o n t section of the A-500 overdrive automatic
transmission is a modified A-999, three speed t r a n s -
mission. The f r o n t section of the A-518 overdrive au-
t o m a t i c transmission is a modified A-727 three speed
transmission.
T h e overdrive u n i t is mounted a t the rear of the
t r a n s m i s s i o n case i n place o f the n o r m a l extension
housing. The overdrive u n i t is connected to the f r o n t
section intermediate shaft. T h e overdrive u n i t pro-
vides a f o u r t h gear r a t i o of 0.69 to 1 (Fig. 1). T h e
f i r s t three gear ratios o f the A-500/518 transmission
are t h e same as those i n the applicable three speed
a u t o m a t i c transmission.
T h e A-500 is used for 3.9L and 5.2L applications.
The A-518 transmission is used for 5.2 and 5.9 L gas
engine applications.
OVERDRIVE
COMPONENTS
The components i n the front section o f t h e A-500/
518 transmission are basically t h e same as those i n
the applicable Chrysler transmission. However, dif-
ferent components are needed t o a t t a c h t h e overdrive
u n i t .
The three speed transmission has a n i n t e r m e d i a t e
shaft instead of the usual o u t p u t shaft. I t serves as
the front section o u t p u t shaft a n d connects the over-
drive u n i t to the front section.
The governor and speedometer drive are relocated
to t h e rear o f the overdrive u n i t o u t p u t shaft. T w o
bearings are used t o support t h e overdrive o u t p u t
shaft. A longer p a r k lock r o d assembly i s also r e -
quired.
R o t a t i n g seal r i n g s and pressurized o i l for the over-
drive and direct clutches i n t h e overdrive u n i t are
not required. The governor is t h e only component re-
ceiving pressurized o i l (through s l i p f i t tubes). Pres-
surized o i l for t h e overdrive l u b r i c a t i o n circuit i s
supplied t h r o u g h the intermediate shaft.
Governor pressure and overdrive pressure taps are
provided i n t h e rear o f the transmission case for i n -
vehicle pressure testing.
The overdrive f o u r t h gear range is provided b y a
t h i r d planetary gear set, a direct clutch, an overdrive
clutch and a n o v e r r u n n i n g clutch. A h i g h tension
spring t h a t exerts u p to 800 pounds (5,516 k P a )
force, holds the sun gear t o t h e a n n u l u s for direct
drive. For coasting or reverse gear, power flows only
t h r o u g h the direct clutch.
The lockup t i m i n g valve releases the torque con-
verter to n o r m a l operation p r i o r to the 4-3 downshift.
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