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16 - 16
DRIVE SHAFTS AND UNIVERSAL JOINTS
•
W h e n angle " B " (Fig. 10) i s too large, i t can be de-
creased b y increasing t h e axle drive p i n i o n gear
shaft angle.
(1) Raise t h e rear o f the vehicle and place support
stands under t h e frame.
(2) Position a h y d r a u l i c j a c k under t h e d i f f e r e n t i a l
housing a n d raise the j a c k j u s t enough t o support t h e
w e i g h t o f the axle.
(3) Remove t h e rear wheels/tires.
(4) Loosen t h e s p r i n g U-bolt nuts.
(5) I n s t a l l tapered shims ( w i t h t h e r e q u i r e d degree
of taper) between t h e springs a n d t h e axle s p r i n g
pads according to t h e following i n s t r u c t i o n s :
• i f angle " B " (Fig. 10) m u s t be increased (i.e., t h e
axle drive p i n i o n gear shaft angle decreased), i n s t a l l
t h e adjustment shims so t h a t t h e t h i c k e n d o f each
s h i m i s facing the front of the vehicle; a n d
• i f angle " B " (Fig. 10) m u s t be decreased (i.e., t h e
axle drive p i n i o n gear shaft angle increased), i n s t a l l
t h e adjustment shims so t h a t t h e t h i c k e n d o f each
s h i m is facing the rear o f the vehicle.
(6) T i g h t e n t h e s p r i n g U-bolt nuts:
• Model 150 a n d 250 vehicles - 6 1 N n n (45 ft-lbs)
torque; a n d
• Model 350 vehicles — 149 N n n (110 ft-lbs) torque.
(7) Remove t h e h y d r a u l i c jack, i n s t a l l t h e wheels/
tires, remove t h e support stands and lower t h e vehi-
cle.
(8) T i g h t e n t h e wheel l u g nuts w i t h t h e specified
torque. Refer t o t h e Torque Specifications c h a r t a t
the end o f Group 22—Tires A n d Wheels for t h e cor-
rect torque value.
HORIZONTAL
ANGLES
I f the drive shaft horizontal angle is n o t zero de-
grees (i.e., the front and rear U-joints are not i n per-
fect l o n g i t u d i n a l alignment), t h e f a u l t i s n o r m a l l y
caused b y rear axle misalignment. D r i v e shaft v i b r a -
t i o n can also result from rear axle m i s a l i g n m e n t .
FRONT YOKE MEASUREMENT
Horizontal drive shaft a l i g n m e n t is as i m p o r t a n t as
vertical alignment. The required tools are:
• straightedge t h a t is 20 to 40 inches (508 t o 1016
m m ) longer t h a n the rear wheel t r a c k (i.e., t h e v e h i -
cle w i d t h ) ;
• short straightedge;
• t w o large and t w o s m a l l C-clamps;
• r i g i d tape measure; a n d
• large carpenter's square.
(1) Inspect the condition of the engine rear mounts.
Worn/loose
engine
or transmission/transfer
case
mounts could cause m i s a l i g n m e n t and cause a n erro-
neous measurement.
(2) Position the vehicle on level surface or level t h e
vehicle (to eliminate t h e possibility o f a n incorrect
measurement).
(3) C l a m p t h e long straightedge a t r i g h t (90°) a n -
gles t o t h e frame r a i l s (Fig. 13). To verify, measure
the
9 0 degree angle
w i t h
t h e large
carpenter's
square.
Fig. 13 Horizontal Alignment Measurement
(4) C l a m p a short straightedge t o t h e front yoke
arms so t h a t i t is p a r a l l e l to t h e surface (Fig. 13).
V e r i f y t h a t t h e straightedge is level w i t h a s p i r i t
level. I t m u s t be exactly level for accurate measure-
ments.
(5) Measure t h e distance " X " between t h e t w o
straightedges f r o m both ends o f t h e short s t r a i g h t -
edge w i t h t h e tape measure (Fig. 13). T h e tape m u s t
be h e l d p a r a l l e l to t h e sides of vehicle frame r a i l .
(6) T h e t w o lengths should be w i t h i n
1/16 of-
an-inch (1.58 m m ) of each other. I f t h e y are not, t h e
drive shaft front yoke is not properly aligned.
(7) T h e Horizontal alignment o f ' t h e transmission/
transfer case yoke can be measured i n same manner
as described above, however, substitute a s t r a i g h t
piece o f r o u n d b a r stock for t h e short straightedge.
Ensure t h a t t h e b a r fits " s n u g " i n yoke a r m bores.
Otherwise, drive a wooden wedge between t h e b a r
and t h e yoke shaft.
REAR AXLE AND AXLE YOKE HORIZONTAL
MEASUREMENT
W h e n a vehicle does not t r a c k s t r a i g h t (i.e., "dog-
t r a c k s " ) , rear axle mis-alignment is a common cause.
The m i s - a l i g n m e n t usually results f r o m loose spring
U-bolt nuts, w h i c h allows the s p r i n g center bolt to be
"sheared-off" and the axle spring pad to shift forward
or r e a r w a r d on t h e adjacent spring leaf. The exist-
ence o f rear axle mis-alignment can be determined
by accurately measuring t h e distance from a fixed
point o n t h e frame r a i l to the center l i n e of the axle
shaft t u b e on each side of the vehicle. I f t h e mea-
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