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DRIVE SHAFTS AND UNIVERSAL JOINTS
16 - 16
i n s t a l l i n g tapered shims between t h e rear springs
and t h e o f rear axle spring pads.
MEASUREMENT
(1) Shift t h e transmission t o t h e N E U T R A L posi-
t i o n .
(2) Raise t h e vehicle on a t w i n post or a s i m i l a r
type hoist t h a t w i l l support the vehicle a t t h e axles
and allow the wheels t o be rotated.
I f a d r i v e - o n t y p e
( p l a t f o r m )
h o i s t i s u s e d ,
p l a c e s u p p o r t s t a n d s u n d e r e a c h a x l e s h a f t t u b e
a n d l o w e r t h e h o i s t u n t i l t h e w h e e l s w i l l r o t a t e
freely.
(3) Rotate the rear drive shaft u n t i l the t r a n s m i s -
sion/transfer case yoke is i n t h e vertical position
(Fig. 12).
(4) Place a level protractor o n the front yoke and
bearing cap " A " (parallel t o t h e drive shaft). Adjust
t h e protractor so t h e bubble i n spirit level i s cen-
tered. Note the angle on the protractor scale.
(5)
Repeat
t h e same
measurement
procedure
(above) for the center yoke and bearing cap " B " , and
for the rear yoke and bearing cap "C". Note b o t h an-
gles o n t h e protractor scale.
(6) Excessive v a r i a t i o n i n measured angles " A " ,
" B " and " C " indicates drive shaft vertical m i s - a l i g n -
ment. T h e vertical
a l i g n m e n t o f two-piece
drive
shafts a t t h e yokes should be greater t h a n one-half
degree (1/2°) and retained as close t o one dfegree (1°)
as possible.
(7) D r i v e shaft v i b r a t i o n t h a t is not associated w i t h
unbalance or " r u n o u t " (e.g., decreasing or increasing
as engine speed increases) i s h i g h l y responsive t o
rear axle drive p i n i o n gear shaft yoke angle adjust-
ment. T h i s
includes
t h e center
b e a r i n g
support
l e n g t h adjustment for two-piece d r i v e shafts.
(8) A d j u s t m e n t o f the drive p i n i o n gear shaft yoke
v e r t i c a l angle is accomplished b y i n s t a l l i n g tapered
shims between t h e rear springs a n d t h e rear axle
spring pad, and/or correcting the center b e a r i n g sup-
port bracket length.
VERTICAL
ANGLE
ADJUSTMENT
The d r i v e shaft v e r t i c a l angle (i.e., angle " A " m i -
nus angle " B " , F i g . 10) i s controlled b y t h e axle drive
p i n i o n gear shaft angle. The axle d r i v e p i n i o n gear
shaft angle is adjusted between t h e rear springs and
the axle w i t h tapered shims. Tapered shims are com-
m e r c i a l l y available
from automotive parts supply
sources.
I f t h e v e r t i c a l angle is not correct a t t h e transmis-
sion (or transfer case) a n d t h e vehicle i s equipped
w i t h a two-piece drive shaft, the center bearing sup-
port should be inspected for the correct l e n g t h . Shims
can be inserted between
t h e support bracket a n d
frame crossmember t o correct mis-alignment, i f nec-
essary.
I f a n g l e " A " m i n u s a n g l e " B " i s g r e a t e r
t h a n
o n e d e g r e e p o s i t i v e ( > +1°), a n g l e " B " ( F i g . 10) i s
t o o s m a l l a n d m u s t b e i n c r e a s e d .
W h e n angle " B " (Fig. 10) is too s m a l l , i t can be i n -
creased b y decreasing
t h e axle d r i v e p i n i o n gear
shaft angle.
I f a n g l e " A " m i n u s a n g l e " B " i s g r e a t e r
t h a n
o n e d e g r e e n e g a t i v e ( > - l ° ) ; a n g l e " B " ( F i g . 10) i s
t o o l a r g e a n d m u s t b e d e c r e a s e d .
YOKES MUST BE IN SAAAE PLANE
J9016-26
Fig. 12 Vertical Angle Measurement— Two-Piece Drive Shaft
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