1999 DODGE RAM Service Repair Manual

DRIV E S H AFTS & " U " J O IN TS - R W D

1999 D odge P ic ku p R 1500
1998-99 Drive Axles
CHRY - Drive Shafts & "U" Joints - RWD Trucks
Dakota, Ram Pickup, Ram Van/Wagon
DESCRIPTION
Drive shafts are balanced, tubular shafts with "U" joints
attached at each end. Flanges or yokes are used to connect drive shaft
"U" joints to rear differential pinion flange or to transmission
output shaft. "U" joint bearing caps are bolted to shaft flanges, or
are pressed into shaft yokes. Drive shafts can be steel or aluminum.
Number of drive shafts used by vehicle depends on vehicle
length and 4WD capability. Long wheel base vehicles use 2 rear drive
shafts with a center bearing support assembly. See Fig. 1. 4WD
applications use a double cardan constant velocity joint on front axle
drive shaft for correct drive shaft-to-front axle alignment. See
Fig. 12 .
Locations of slip joints and splined shafts vary with model
application. Single tube type drive shaft has slip joint on outside of
"U" joint flange/yoke. This slip joint slides in and out on
transmission's splined main shaft.
Fig. 1: Identifying Common Drive Shaft Combinations
Courtesy of Chrysler Corp.
LUBRICATION

Apply multipurpose lubricant (NLGI grade 2 EP) to "U" joints
and slip joint fittings.
INSPECTION
Abnormal vibration and noise can come from many driveline
sources. Drive shaft vibration/noise increases with vehicle speed
(MPH). A vibration that occurs within a specific speed is not caused
by drive shaft imbalance. Before overhauling driveline, check for
other causes/sources of possible vibration/noise.
TIRES & WHEELS
Check tire inflation and wheel balance. Check for foreign
objects in tread, damaged tread, mismatched tread patterns or
incorrect tire sizes. Check for bent wheels.
CENTER BEARING
Tighten drive shaft center bearing mounting bolts. If bearing
insulator is deteriorated or oil-soaked, or drive shaft can be moved
up/down in support, replace center bearing support assembly.
ENGINE & TRANSMISSION MOUNTS
Tighten mounting bolts. If rubber mounts are deteriorated or
broken, replace as needed.
DRIVE SHAFT(S)
Check drive shaft(s) for missing weights, broken welds, or
for dents affecting balance. Check for undercoating, mud, snow/ice on
drive shaft(s). Clean shafts thoroughly and test drive.
"U" JOINTS
Check for foreign material lodged in joints and flange/yokes.
Check for loose "U" joint-to-flange mounting bolts. Check for worn "U"
joint needle bearings. Check for Reddish-Brown rust-dust around "U"
joint caps. Replace "U" joints if necessary.
ADJUSTMENTS
CHECKING DRIVE SHAFT PHASING
One-Piece Drive Shafts
1) Ensure "U" joint flanges on either end of drive shaft are
in same plane. See Fig. 2. Drive shafts with slip joints between yokes
often have arrows to aid in alignment. If yokes are not in same plane,
disassemble slip joint from drive shaft splines. Install slip joint
back onto drive shaft splines, aligning "U" joint yokes. Test drive.
2) Single tube type drive shaft has slip joint on outside of
"U" joint yoke (at transmission end). If one-piece tube type drive
shaft yokes are out of alignment, the drive shaft is torque-twisted.
Drive shaft must be replaced.

Fig. 2: Checking Phase Alignment Of One-Piece Drive Shaft
2-Piece Shafts
1) On most models with 2-piece drive shafts, proper yoke
phasing is accomplished by keys on drive shaft spline and keyway in
slip joint splines. Drive shafts of this type will fit together only
one way. Non-key drive shafts will fit together in any order on
spline.
2) Rotate transmission flange/yoke until flange/yoke ears
(trunnion axis) are in horizontal plane. Install front drive shaft-to-\
transmission flange/yoke keeping flange/yoke in horizontal plane. This
puts both flange/yoke ears of front drive shaft in vertical plane. See
Fig. 3 .
3) Connect center bearing support assembly to crossmember
bracket. Ensure front face of center bearing support assembly is
perpendicular (90
) to center line of drive shaft. If center bearing
support assembly is installed crooked or off center, drive shaft
vibration and/or noise will result. See Fig. 8.
4) Align and install rear drive shaft splines into slip yoke
splines while keeping rear drive shaft flange/yoke in horizontal
plane. Drive shaft rear "U" joint mounting caps will be in vertical
plane. Set differential pinion flange in vertical plane. Connect rear
drive shaft-to-pinion flange. If 2-piece shaft is correctly installed,
center line of flange/yokes trunnion axis for each individual shaft
will be parallel. See Fig. 3.
Fig. 3: Checking Phase Alignment Of 2-Piece Drive Shaft
Courtesy of Chrysler Corp.
CHECKING RUNOUT

1) On drive shafts greater than 30" in length, measure runout
3" from transmission flange/yoke, center bearing yoke and pinion
flange using dial indicator. Maximum runout for Ram Pickup is .030" (.
76 mm) at front and rear end of drive shaft and .035" (.89 mm) at
center of drive shaft. Maximum runout for all other models is .010" (.
25 mm) at front and rear end of drive shaft and .015" (.38 mm) at
center of drive shaft.
2) For drive shafts less than 30" in length, maximum runout
for Pickup is .030" (.76 mm). Maximum runout for all other models is .\
020" (.51 mm). Replace drive shaft if maximum runout is exceeded.
BALANCING DRIVE SHAFT
1) Perform following procedure only after inspecting all
other possible causes of vibration. See INSPECTION. Drive shaft
imbalance may often be cured by disconnecting shaft, rotating it 180
degrees and reconnecting shaft to flange. Test drive to check results.
NOTE: DO NOT run engine for prolonged periods without forced
airflow across radiator. Engine or transmission may
overheat.
2) To balance drive shaft(s), begin by raising rear wheels
off ground and turning drive shaft with engine. Balance testing may be
done by marking drive shaft in 4 positions, 90 degrees apart around
shaft. Place marks about 6" forward of rear flange/yoke weld. Number
marks 1-4.
3) Install large diameter screw-type hose clamp around drive
shaft so clamp's head is in No. 1 position. Spin drive shaft with
engine and note vibrations. If there is little or no change in
vibration intensity, move clamp head to No. 2 position, and repeat
test.
4) Continue procedure until vibration is at lowest level. If
no difference is noted with clamp head moved to all 4 positions,
vibrations may not be due to drive shaft imbalance.
5) If vibration decreases but is not completely eliminated,
place a second clamp at same position, and repeat test. Combined
weight of both clamps in one position may increase vibration. If so,
rotate clamps 1/2" apart, above and below lowest vibration level
position, and repeat test.
6) Continue to rotate clamps, as necessary, until vibration
is at lowest point. If vibration can be eliminated or reduced to
acceptable level, bend back slack end of clamp so screw cannot loosen.
If vibration level is still unacceptable, leave rear clamp(s) in
place, and repeat procedure at front end of drive shaft. Road test
vehicle. On 4WD models, perform procedure on each shaft.
CHECKING VERTICAL ANGLE
One-Piece Drive Shafts
1) Raise and support vehicle so rear wheels can be rotated.
Rotate drive shaft so a pinion flange bearing cap faces downward.
Attach Inclinometer (C-4224) magnet to bearing cap, and measure drive
shaft vertical angle. See Fig. 4. Remove inclinometer.
2) Rotate drive shaft 90 degrees until drive shaft rear yoke
bearing cap faces downward. Attach inclinometer magnet to bearing cap,
and measure drive shaft vertical angle. Difference between 2 measured
angles is drive shaft rear angle. See Fig. 5. Remove inclinometer.
3) Rotate drive shaft until a slip joint yoke bearing cap
faces downward. Attach inclinometer magnet to bearing cap, and note
angle. Remove inclinometer. Rotate drive shaft 90 degrees until drive
shaft front yoke bearing cap faces downward. Attach inclinometer
magnet to bearing cap, and note angle. Remove inclinometer.

4) Difference between 2 measured angles is drive shaft front
angle. See Fig. 5. Compare front and rear angles. Allowable difference
between angles is plus or minus one degree. If difference of angles is
greater than specified, adjustment is necessary. See ADJUSTING
VERTICAL ANGLE.
Fig. 4: Measuring Drive Shaft Vertical Angle
Courtesy of Chrysler Corp.
Fig. 5: Identifying Front & Rear Vertical Angle
Courtesy of Chrysler Corp.
2-Piece Non-Parallel Drive Shafts (Broken-Back Type)
1) A broken-back type driveline is where yokes are not

perpendicular to each other in vertical plane. See Fig. 6. With non-
parallel or broken-back type installation, working angles of "U"
joints of given drive shaft must be equal (angle "A" = angle "B").
Fig. 6: Identifying Broken-Back Type Drive Shaft
Courtesy of Chrysler Corp.
2) Calculate by subtracting angle of output shaft center line
from angle of drive shaft. Difference should be equal to front shaft
angle subtracted from rear shaft angle.
2-Piece Drive Shafts (Except Broken-Back Type)
1) All yokes must be perpendicular in both vertical and
horizontal planes to engine crankshaft. Using Inclinometer (C-4224),
measure drive shaft vertical angles.
2) Raise and support vehicle so rear wheels can be rotated.
Rotate drive shaft so a pinion flange bearing cap faces downward.
Attach inclinometer magnet to bearing cap, and note angle. See Fig. 4.
Remove inclinometer.
3) Rotate drive shaft 90 degrees until drive shaft rear yoke
bearing cap faces downward. Attach inclinometer magnet to bearing cap,
and note angle. Difference between 2 measured angles is drive shaft
rear angle. See Fig. 5. Remove inclinometer.
4) Rotate drive shaft until a slip joint yoke bearing cap
faces downward. Attach inclinometer magnet to bearing cap, and note
angle. Remove inclinometer. Rotate drive shaft 90 degrees until drive
shaft front yoke bearing cap faces downward. Attach inclinometer
magnet to bearing cap, and note angle. Difference between 2 measured
angles is drive shaft front angle. See Fig. 5. Remove inclinometer.
5) Rotate drive shaft until front yoke of rear shaft faces
downward. Attach inclinometer magnet to bearing cap, and note angle.
Rotate drive shaft until rear yoke of front drive shaft faces
downward. Attach inclinometer magnet to bearing cap, and note angle.
Remove inclinometer.
6) Difference between 2 measured angles is drive shaft center
angle. Compare front, center and rear angles. Vertical alignment of 2
piece drive shafts at yokes should be greater than 1/2 degree and must
be retained as close to one degree as possible. See Fig. 7. If
difference of angles is greater than specified, adjustment is
necessary. See ADJUSTING VERTICAL ANGLE.

Fig. 7: Checking Vertical Alignment Of 2-Piece Drive Shaft
Courtesy of Chrysler Corp.
ADJUSTING VERTICAL ANGLE
If front angle minus rear angle is greater than one degree
positive (+1 degree), rear angle is too small and must be increased.
If front angle minus rear angle is greater than one degree negative (-
1 degree), rear angle is too large and must be decreased.
1) Raise and support rear of vehicle. Position a jack under
differential housing. Remove rear wheel assemblies. Loosen rear spring
"U" bolt nuts. Insert tapered shim between spring and axle spring pad.
If increasing angle, insert shim with taper facing front of vehicle.
If decreasing angle, insert shim with taper facing rear of vehicle.
NOTE: If encountering difficulty in making drive shaft vertical
adjustments on one-piece drive shafts, drive shaft may be out
of horizontal alignment. See CHECKING HORIZONTAL ALIGNMENT.
NOTE: On 2-piece drive shafts, center angle is adjusted by use of
shims between center support mounting bracket and frame
crossmember. Center angle may need adjusting if rear angle is
changed.
2) Tighten spring "U" bolt nuts to specification. See TORQUE
SPECIFICATIONS table. Recheck drive shaft angle measurements. See
CHECKING VERTICAL ANGLE.
CHECKING HORIZONTAL ALIGNMENT
1) Drive shaft horizontal alignment should be checked if
frame damage is suspected or when major components have been replaced.
See Fig. 8 .
2) Clamp a long straightedge (12" longer than width of rear
wheel track) at 90 degrees to frame side rails. See Fig. 9. Use large
framing squares to align straightedge with side rails.

Fig. 8: Identifying Horizontal Misalignment Of Drive Shaft
Courtesy of Chrysler Corp.
Fig. 9: Checking Horizontal Alignment
Courtesy of Chrysler Corp.
3) To make horizontal alignment checks, set up straightedges
as shown. See Fig. 9. Set transmission output flange/yoke