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FRONT SUSPENSION
2 - 25
DISCONNECT AXLE VACUUM CONTROL SYSTEM
SERVICE
DESCRIPTION
The disconnect axle v a c u u m control system consists
of a vacuum control s w i t c h o n t h e transfer case, a n
a i r vent f i l t e r , a v a c u u m shift motor (located on the
left front axle tube), a 4 W D indicator l i g h t and vac-
u u m switch, t w o v a c u u m check valves, a reservoir
and a n interconnecting v a c u u m harness (Fig. 22).
FILTER
J8902-52
Fig. 22 Disconnect Axle Vacuum Control System
R e f e r t o G r o u p 2 1 f o r a d d i t i o n a l s e r v i c e i n f o r -
m a t i o n i n v o l v i n g t h e d i s c o n n e c t a x l e c o n t r o l sys-
t e m .
AXLE SHIFT MOTOR FUNCTIONAL
TEST
(1) Raise and support t h e vehicle. Disconnect t h e
vacuum harness f r o m t h e axle shift motor and con-
nect a v a c u u m pump t o the v a c u u m shift motor front
port (Fig. 23).
(2) A p p l y 5 1 kPa (15 i n . H g ) o f v a c u u m t o the front
port and rotate the left front wheel to f u l l y disengage
the inner and intermediate axle shafts (i.e., shift t o
two-wheel drive operation).
(3) T h e shift motor should m a i n t a i n t h e vacuum
applied t o t h e front port for a m i n i m u m o f 30 sec-
onds. I f t h e motor does not m a i n t a i n the vacuum, re-
place i t . I f t h e motor does m a i n t a i n t h e vacuum,
proceed t o the next step.
(4) Disconnect the vacuum p u m p f r o m t h e vacuum
shift motor front p o r t (Fig. 23). Connect t h e vacuum
REAR
PORT
MOTOR
J8902-57
Fig. 23 Axle Vacuum Shift Motor
p u m p t o t h e v a c u u m s h i f t motor rear port, cap t h e
port for t h e 4 W D indicator l a m p switch, and apply 51
k P a (15 i n . H g ) of v a c u u m t o the rear port.
(5) T h e shift motor should m a i n t a i n t h e vacuum
applied t o the rear p o r t for a m i n i m u m o f 30 seconds.
I f t h e shift motor does not m a i n t a i n the vacuum, re-
place i t . I f the motor does m a i n t a i n the vacuum, pro-
ceed t o t h e n e x t step.
(6) Remove t h e cap f r o m t h e port for t h e 4 W D i n -
dicator l a m p s w i t c h a n d determine i f vacuum was
present a t t h i s port. I f v a c u u m was present, the shift
motor
functions
n o r m a l l y .
I f vacuum
was
n o t
present, proceed t o t h e n e x t step.
(7) A p p l y 5 1 k P a (15 i n . H g ) o f vacuum to the shift
motor rear port. Rotate t h e left front wheel as neces-
sary and ensure t h a t t h e i n n e r and intermediate axle
shafts are completely engaged. T h e axles m u s t be
completely engaged (i.e., shifted to 4 W D operation) t o
open the p o r t for the 4 W D indicator lamp switch.
(8) Determine i f v a c u u m is present a t the port for
the 4 W D indicator l a m p switch again. I f vacuum was
present a t t h e port, t h e shift motor functions nor-
m a l l y . I f v a c u u m was not present a t the port, replace
the shift motor.
(9) Connect t h e v a c u u m harness t o the shift motor
(Fig. 24), remove t h e supports and lower the vehicle.
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