1994 JEEP CHEROKEE Service Repair Manual

shaft must be able to change operating angles when
going over various road surfaces. This is done
through universal joints, which permit the propeller
shaft to operate at different angles. The slip joints (or
yokes) permit contraction or expansion (Fig. 1,2).
Tubular propeller shafts are balanced by the man-
ufacturer with weights spot welded to the tube.
The propeller shaft is designed and built with the
yoke lugs in line with each other which is called
phasing. This design produces the smoothest running
condition, an out of phase shaft can cause a vibra-
tion.
Before undercoating a vehicle, the propeller
shaft and the U-joints should be covered. This
will prevent the undercoating from causing an
unbalanced condition and vibration.
CAUTION: Use exact replacement hardware for at-
taching the propeller shafts. The specified torque
must always be applied when tightening the fasten-
ers.
UNIVERSAL JOINTS
Two different types of U-joints are used with the
propeller shafts:
²Single cardan U-joint (Fig. 3)
²Double cardan U-joint (Fig. 4)
LUBRICATION
The slip yoke and certain universal joints are
equipped with zerk type lubrication fittings. They
should be lubricated with a multi-purpose NLGI
Grade 2 EP lubricant. All U-joints should be in-
spected for leakage and damage each time the vehi-
cle is serviced. If seal leakage or damage exists, the
U-joint should be replaced.
Fig. 3 Single Cardan Universal Joint
Fig. 4 Double Cardan (CV) Universal Joint
16 - 2 PROPELLER SHAFTSJ

SERVICE DIAGNOSIS/PROCEDURES
INDEX
page page
Runout................................. 4
Unbalance............................... 3Universal Joint Angle Measurement............ 4
Vibration................................ 3
VIBRATION
Tires that are out-of-round or wheels that are un-
balanced will cause a low frequency vibration. Refer
to Group 22, Wheels and Tires for additional infor-
mation.
Brake drums that are unbalanced will cause a
harsh, low frequency vibration. Refer to Group 5,
Brakes for additional information.
Driveline vibration can also result from loose or
damaged engine mounts. Refer to Group 21, Trans-
missions for additional information.
Propeller shaft vibration will increase as the vehi-
cle speed is increased. A vibration that occurs within
a specific speed range is not caused by propeller
shaft unbalance. Defective universal joints or an in-
correct propeller shaft angle are usually the cause.
UNBALANCE
If propeller shaft unbalance is suspected, it can be
verified with the following procedure.
Removing and re-indexing the propeller shaft
180É may eliminate some vibrations.
²Clean all the foreign material from the propeller
shaft and the universal joints.²Inspect the propeller shaft for missing balance
weights, broken welds, and bent areas.If the pro-
peller shaft is bent, it must be replaced.
²Ensure the universal joints are not worn, are prop-
erly installed, and are correctly aligned with the
shaft.
²Check the universal joint clamp screws torque
(1) Raise the vehicle.
(2) Remove the wheel and tires assembly. Install
the wheel lug nuts to retain the brake drums.
(3) Mark and number the shaft six inches from the
yoke end at four positions 90É apart.
(4) Run and accelerate the vehicle until vibration
occurs. Note the intensity and speed the vibration oc-
curred. Stop the engine.
(5) Install a screw clamp at position 1 (Fig. 1).
(6) Start the engine and re-check for vibration. If
there is little or no change in vibration, move the
clamp to one of the other three positions. Repeat the
vibration test.
(7) If there is no difference in vibration at the
other positions, the vibration may not be propshaft
unbalance.
DRIVELINE VIBRATION
JPROPELLER SHAFTS 16 - 3

(8) If the vibration decreased, install a second
clamp (Fig. 2) and repeat the test.
(9) If the clamps cause an additional unbalance,
separate the clamps (1/4 inch above and below the
mark). Repeat the vibration test (Fig. 3).(10) Increase distance between the clamp screws
and repeat the test until the amount of vibration is
at the lowest level. Bend the slack end of the clamps
so the screws will not loosen.
(11) Install the wheel and tires. Lower the vehicle.
(12) If the amount of vibration remains unaccept-
able, apply procedures at the front end of the propel-
ler shaft.
RUNOUT
(1) Remove dirt, rust, paint, and undercoating
from the propeller shaft surface. Areas where the
dial indicator will contact the shaft must be clean.
(2) The dial indicator must be installed perpendic-
ular to the shaft surface.
(3) Measure runout at the center and ends away
from welds.
(4) Refer to Runout Specifications chart.
(5) Replace the propeller shaft if the runout ex-
ceeds the limit.
UNIVERSAL JOINT ANGLE MEASUREMENT
INFORMATION
When two shafts come together at any common
joint, the bend that is formed is called the operating
angle. The larger the angle, the larger the amount of
acceleration and deceleration of the joint. This speed-
ing up and slowing down of the joint must be can-
celled to produce a smooth power flow. This is done
through phasing and proper universal joint working
angles.
A propeller shaft is properly phased when the yoke
ends are on the same plane or in line. A twisted
shaft will throw the yokes out of phase and cause a
noticeable vibration.
When taking universal joint angle measurements
or checking phasing with two piece shafts, consider
each shaft separately. On 4WD vehicles, the front
shaft input (pinion shaft) angle has priority over the
caster angle.
Ideally the driveline system should have;
²Angles that are in equal or opposite within 1 de-
gree of each other
Fig. 1 Clamp Screw At Position 1
Fig. 2 Two Clamp Screws At The Same Position
Fig. 3 Clamp Screws Separated
RUNOUT SPECIFICATIONS
16 - 4 PROPELLER SHAFTSJ

²Have a 3 degree maximum operating angle
²Have at least a 1/2 degree continuous operating
(propeller shaft) angle
Engine speed (R.P.M.) is the main factor though in
determining maximum allowable operating angles.
As a guide to maximum normal operating angles re-
fer to the chart listed (Fig. 4).
INSPECTION
Before measuring universal joint angles, the
following must be done.
²Inflate all tires to correct pressure
²Check angles in the same loaded or unloaded con-
dition as when the vibration occurred. Propshaft an-
gles will change according to the amount of load in
the vehicle. Always check angles in loaded and un-
loaded conditions.
²Check the condition of all suspension components
and verify all fasteners are torqued to specifications.
²Check the condition of the engine and transmis-
sion mounts and verify all fasteners are torqued to
specifications.
MEASUREMENT
To accurately check driveline alignment, raise and
support the vehicle at the axles as level as possible.
Allow the wheels and propeller shaft to turn. Remove
any external bearing snap rings (if equipped) from
universal joint so protractor base sits flat.
(1) Rotate the shaft until transmission/transfer
case output yoke bearing is facing downward.
Always make measurements from front to
rear.
(2) Place Inclinometer on yoke bearing (A) parallel
to the shaft (Fig. 5). Center bubble in sight glass and
record measurement.
This measurement will give you the transmis-
sion or OUTPUT YOKE ANGLE (A).
(3) Rotate propeller shaft 90 degrees and place In-
clinometer on yoke bearing parallel to the shaft (Fig.
6). Center bubble in sight glass and record measure-
ment. This measurement can also be taken at the
rear end of the shaft.
This measurement will give you the PROPEL-
LER SHAFT ANGLE (C).(4) Subtract smaller figure from larger (C minus A)
to obtain transmission OUTPUT OPERATING AN-
GLE.
(5) Rotate propeller shaft 90 degrees and place In-
clinometer on pinion yoke bearing parallel to the
shaft (Fig. 7). Center bubble in sight glass and record
measurement.
This measurement will give you the pinion
shaft or INPUT YOKE ANGLE (B).
(6) Subtract smaller figure from larger (C minus
B) to obtain axle INPUT OPERATING ANGLE.
Refer to rules given below and the example in (Fig.
8) for additional information.
Fig. 4 Maximum Angles and R.P.M.
Fig. 5 Front (Output) Angle Measurement (A)
Fig. 6 Propeller Shaft Angle Measurement (C)
JPROPELLER SHAFTS 16 - 5

²Good cancellation of u-joint operating angles (with-
in 1É)
²Operating angles less than 3É
²At least 1/2 of one degree continuous operating
(propeller shaft) angle
ADJUSTMENT AT AXLE WITH LEAF SPRINGS
Adjust the pinion shaft angle at the springs with
tapered shims (Fig. 9). Install tapered shims between
the springs and axle pad to correct the angle. Refer
to Group 3, Rear Suspension and Axle for additional
information.
Fig. 8 Universal Joint Angle Example
Fig. 7 Rear (Input) Angle Measurement (B)
Fig. 9 Angle Adjustment at Leaf Springs
16 - 6 PROPELLER SHAFTSJ

ADJUSTMENTÐXJ FRONT SHAFT
Adjust the pinion gear angle at the lower suspen-
sion arms with shims (Fig. 10). Adding shims will de-
crease the pinion gear shaft angle but will increase
the caster angle. The pinion gear shaft angle has pri-
ority over the caster angle.
PROPELLER SHAFT REPLACEMENT
PRECAUTIONS
Use exact replacement hardware for attaching the
propeller shafts. Exact replacement will ensure safe
operation. The specified torque must always be ap-
plied when tightening the fasteners.
Put reference marks on the propshaft yoke and axle
or transmission yoke before service (Fig. 1). This will
assure correct phasing and eliminate possible vibration.
CAUTION: Do not allow the propeller shaft to drop
or hang from either universal joint during removal.
Attach it to the vehicle underside with wire to pre-
vent damage to the universal joints.CAUTION: It is very important to protect the ma-
chined, external surface of the slip yoke from dam-
age after propeller shaft removal. If damaged, the
transmission extension seal could be damaged and
cause a leak.
FRONTÐXJ VEHICLES
REMOVAL
(1) Raise the vehicle.
(2) Scribe alignment marks on the yokes at the
transfer case. Place marks at the pinion shaft and at
each end of the propeller shaft. These marks will be
used for installation reference (Fig. 2).
(3) Remove the U-joint strap bolts at the pinion
shaft yoke.
(4) Disconnect the propeller shaft at the transfer
case and remove the propeller shaft.
INSTALLATION
(1) Position the propeller shaft with the yoke refer-
ence marks aligned (Fig. 1). Install the propeller
shaft.
Replacement U-joint straps and bolts must be
installed.
(2) Tighten the U-joint strap/clamp bolts at the
axle yoke to 19 Nzm (14 ft. lbs.) torque.
(3) Tighten the flange to transfer case bolts to 27
Nzm (19.5 ft. lbs.) torque.
(4) Lower the vehicle.
Fig. 10 Angle AdjustmentÐXJ Vehicles
Fig. 1 Reference Marks on Yokes
JPROPELLER SHAFTS 16 - 7

REARÐXJ,YJ VEHICLES
REMOVAL
(1) Shift the transmission and transfer case (if ap-
plicable) to their Neutral positions. Raise the vehicle.
(2) Scribe alignment marks at the pinion shaft and
at each end of the propeller shaft. These marks will
be used for installation reference.
(3) Remove the U-joint strap bolts at the pinion
shaft yoke.
(4) Slide the slip yoke off of the transmission/
transfer case output shaft and remove the propeller
shaft (Fig. 3).
INSTALLATION
(1) Slide the slip yoke on the transmission/transfer
case output shaft. Align the installation reference
marks at the axle yoke and install the propeller shaft
(Fig. 3).
Replacement U-joint straps and bolts must be
installed.
(2) Tighten the U-joint strap/clamp bolts at the
axle yoke to 19 Nzm (14 ft. lbs.) torque.
(3) Lower the vehicle.
FRONTÐYJ VEHICLES
REMOVAL
(1) Raise the vehicle.
(2) Scribe alignment marks on the yokes at the
transfer case. Place marks at the pinion shaft and at
each end of the propeller shaft. These marks will be
used for installation reference (Fig. 4).(3) Remove the U-joint strap bolts at the pinion
shaft yoke.
(4) Disconnect the propeller shaft at the transfer
case and remove the propeller shaft.
INSTALLATION
(1) Position the propeller shaft with the reference
marks aligned (Fig. 4). Install the propeller shaft.
Replacement U-joint straps and bolts must be
installed.
(2) Tighten the U-joint strap/clamp bolts at the
axle yoke to 19 Nzm (14 ft. lbs.) torque.
(3) Tighten the U-joint strap/clamp to transfer case
bolts to 27 Nzm (19.5 ft. lbs.) torque.
(4) Tighten the U-joint strap bolts to 19 Nzm (14 ft.
lbs.) torque.
(5) Lower the vehicle.
Fig. 3 Rear Propeller Shaft
Fig. 4 YJ Front Propeller Shaft
Fig. 2 Front Propeller Shaft
16 - 8 PROPELLER SHAFTSJ

UNIVERSAL JOINT REPLACEMENT
PRECAUTIONS
It is very important to put reference marks on the
yokes before removal or component service (Fig. 1).
This will assure correct phasing and eliminate possi-
ble vibration.
SINGLE CARDAN
REMOVAL/DISASSEMBLY
Single cardan universal joints are not serviceable.
If worn or leaking, they must be replaced as a unit.
(1) Remove the propeller shaft. Refer to Propeller
Shaft Replacement in this Group.
(2)Paint or score alignment marks on the yokes
and propeller shaft for installation reference.
(3) Using a soft drift, tap the outside of the bear-
ing assembly to loosen snap ring.
(4) Remove snap rings from both sides of yoke
(Fig. 2).
(5) Set the yoke in an arbor press or vise with a large
socket beneath it. Position the yoke with the lube fit-
ting pointing up (if equipped). Place a smaller socket on
the upper bearing assembly and press it through to re-
lease the lower bearing assembly (Fig. 3).
(6) If the bearing assembly will not pull out by
hand after pressing, tap the base of the lug near it to
dislodge.
(7) To remove the opposite bearing, turn the yoke
over and straighten the cross in the open hole. Then
carefully press the end of the cross until the remain-
ing bearing can be removed (Fig. 4).
CAUTION: If the cross or bearing assembly are cocked
when being pressed, the bearing assembly will score
the walls of the yoke bore and ruin the yoke.
CLEANING AND INSPECTION
(1) Clean all the universal joint yoke bores with
cleaning solvent and a wire brush.
(2) Inspect the yokes for distortion, cracks and
worn bearing assembly bores.
ASSEMBLY/INSTALLATION
(1) Apply extreme pressure (EP) N.L.G.I. Grade 1
or 2 grease to aid in installation.
(2) Position the cross in the yoke with its lube fit-
ting (if equipped) pointing up (Fig. 5).
(3) Place a bearing assembly over the trunnion and
align it with the cross hole (Fig. 6). Keep the needle
bearings upright in the bearing assembly. A needle
roller lying at the bottom will prevent proper assembly.
Fig. 1 Reference Marks on Yokes
Fig. 2 Remove Snap Ring
Fig. 3 Press Out Bearing
JPROPELLER SHAFTS 16 - 9