Buick LeSabre 1965 Service Manual page 421

PROPELLER SHAFT, 45, 4 6 , 4 8
f
& 4 9 0 0 0 SERIES
6-55
ft. lbs., 49000 only. On 45, 46,
48000 install four bolts at center
bearing support to frame cross
member and torque to 17-23 ft.
lbs.
NOTE: Before torquing bolts, po-
sition propeller shaft rearward
to provide approximately 1/2"
s p a c e between the end of the
transmission case extension and
the shoulder of the propeller shaft
slip yoke.
8. Make certain propeller shaft
slip spline and center ball stud
seat are f u l l y lubricated with
Multi-Purpose Grease EP No. 1
Grade. See paragraphs 1-3 and
1-4 for lubricating procedure.
6-28 ADJUSTMENT OF
REAR UNIVERSAL
JOINT ANGLE—
45, 46, 48000
When torque is t r a n s m i t t e d
through any ordinary universal
joint, the driven yoke fluctuates
slightly in speed. In other words,
although the driving yoke rotates
at a constant speed, the driven
yoke speeds-up and slows-down
twice per revolution. This fluc-
tuation of the driven yoke is in
direct proportion to the angle
through which the universal joint
is operating; the g r e a t e r the
angle, the greater the fluctuation.
Whenever two universal joints are
used, this fluctuation effect can
be eliminated by staggering the
joints so that the two driving
yokes are 90° apart providing the
two joints are transmitting torque
through the same angle.
Therefore, when two universal
joints are used, the a n g l e s
through which they operate must
be very nearly the same. This
allows the alternate acceleration
and deceleration of one joint to
be offset by the alternate decel-
eration and acceleration of the
second joint. When the two joints
do not run at approximately the
same angle, operation is rough
and an objectionable vibration is
produced.
In addition, universal joints are
designed to operate safely and
efficiently within certain angles.
If the designed angle is exceeded,
the joint may be broken or other-
wise damaged.
The front universal joint angle is
actually the angle b e t w e e n the
engine - transmission centerline
and the front p r o p e l l e r shaft.
This angle is determined by the
design of the body a s s e m b l y .
Since this angle is not liable to
change with use, there is norm-
ally no need to change this angle.
The center constant velocity uni-
versal joint, just as the name
implies, transmits at a constant
velocity regardless of the angle
through which it is operating.
Therefore, no means is provided
or needed for adjusting the con-
stant velocity joint.
However, the rear universal joint
angle can vary and must be ad-
justed. It is adjusted by rotating
the rear axle housing; this is ac-
complished by lengthening or
shortening the upper control arms
by means of shimming at the
frame bracket ends. See Figure
6-113.
If drive line shudder, roughness,
vibration, or rumble is experi-
enced, it may be due to incorrect
rear universal joint angle and
this a n g l e should be checked.
Also if there is a severe rear end
collision, or if the axle housing
Figure 6-113—Shimming Upper Control
Arm for Pinion Angle Adjustment
or any control arms are replaced,
the rear universal joint angle
should be checked and corrected
if necessary.
A simple method has been de-
veloped for measuring rear uni-
versal joint angle u s i n g a
spring-loaded steel cable stretch-
ed between the front of the chassis
and the rear axle carrier. When
the rear universal joint angle is
adjusted correctly, this s t e e l
cable will clear the underside of
the pinion flange by a definite
amount. Therefore, if this single
d i r e c t measurement is within
specified limits, the rear univer-
sal joint angle is correct; if this
measurement is out of limits,
the joint angle is not correct.
See Figure 6-114.
Rear universal joint angle is
checked u s i n g Alignment Set
J-8973. The Alignment Height
Tubes J-8973-19 in this set are
designed to raise the rear of the
car slightly above normal trim
height. Use of these tubes makes
sure that the rear universal joint
angle will be checked at a pre-
determined trim height.
The front end of the cable is
equipped with two a t t a c h i n g
brackets so that the cable may
be used on all series 1965 Buicks.
The rear end of the cable has
stops attached at various points
to allow the cable to be placed
in t e n s i o n on a l l wheelbase
Buicks.
a. Checking Rear Universal
Joint Angle
Check rear universal joint angle
using the following procedure:
1. Raise car, preferably on a
drive-on hoist. Install Alignment
Height Tubes J-8973-19 by rais-
ing the rear of the body slightly
while inserting tubes vertically
between frame and axle housing.
See Figure 6-114. If the body does
not come down firmly on the
tubes, add weight in the trunk
until the tubes are held tightly.