check engine DODGE RAM 2001 Service User Guide

²Change front axle fluid (4x4).
²Inspect exhaust system.
111,000 Miles (178 000 km)
²Change engine oil.
²Replace engine oil filter.
²Inspect engine coolant level, hoses, and clamps.
²Flush and replace engine coolant.
²Inspect brake hoses.
²Lubricate the steering linkages.
²Check manual transmission fluid level.
²Inspect exhaust system.
114,000 Miles (182 000 km)
²Change engine oil.
²Replace engine oil filter.
²Inspect engine coolant level, hoses, and clamps.
²Inspect brake hoses.
²Lubricate the steering linkages.
²Check manual transmission fluid level.
²Inspect exhaust system.
117,000 Miles (187 000 km)
²Change engine oil.
²Replace engine oil filter.
²Inspect engine coolant level, hoses, and clamps.
²Inspect brake hoses.
²Lubricate the steering linkages.
²Check manual transmission fluid level.
²Inspect exhaust system.
120,000 Miles (192 000 km)
²Replace engine air cleaner element.
²Replace ignition cables.
²
Inspect PCV valve and replace as necessary.*
²Replace spark plugs.
²Inspect auto tension drive belt and replace if
required.**
²Change engine oil.
²Replace engine oil filter.
²Inspect engine coolant level, hoses, and clamps.
²Inspect brake hoses.
²Inspect brake linings.
²Lubricate the steering linkages.
²Change automatic transmission fluid, filter and
adjust the bands.
²Check manual transmission fluid level.
²Change rear axle fluid.
²Change front axle fluid (4x4).
²Inspect exhaust system.
*This maintenance is recommended by Daimler-
Chrysler to the customer but it is not required to
maintain warranty on the PCV valve.
**This maintenance is not required if the belt was
previously replaced.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
DESCRIPTION - MEDIUM DUTY TRUCK
MAINTENANCE SCHEDULE (8.0L 2500 & 3500
MODELS Ð CALIFORNIA ONLY)
There are two maintenance schedules that show
proper service based on the conditions that the vehi-
cle is subjected to. Use the schedule that best
describes these conditions.
ScheduleªAº, lists all the scheduled maintenance
to be performed under normal operating conditions
for Medium Duty vehicles.
ScheduleªBº, lists maintenance recommended for
Medium Duty vehicles operated under the conditions
listed at the beginning of that schedule.
²Where the time and mileage are listed, follow
the interval that occurs first.
At Each Stop For Fuel
²Check engine oil level and add as required.
²Check windshield washer solvent and add as
required.
²Clean windshield and wiper blades as required.
Once A Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect battery and clean and tighten terminals
as required.
²Check fluid levels of coolant reservoir, brake
master cylinder, power steering, and transmission
and add as needed.
²Check all lights and all other electrical items for
correct operation.
²
Inspect and clean wiper blades. Replace if required.
At Each Oil Change
²Inspect exhaust system.
²Inspect brake hoses.
²Adjust rear brakes.
²Rotate the tires at each oil change interval
shown on schedule ªAº (6,000 Miles) or every other
interval shown on schedule ªBº (6,000 Miles)
²Check engine coolant level, hoses and clamps.
²Lubricate steering linkage.
EMISSION CONTROL SYSTEM MAINTENANCE
The scheduled emission maintenance listed inbold
typeon the Maintenance Schedules, must be done at
the mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
BR/BELUBRICATION & MAINTENANCE 0 - 13
MAINTENANCE SCHEDULES (Continued)

FLUID FILL LOCATIONS AND LUBRICATION
POINTS
The fluid fill/check locations and lubrication points
are located in each applicable group.
MEDIUM DUTY SCHEDULE ªAº
6,000 miles (10 000 km) or at 6 months
²Replace engine oil and filter.
12,000 Miles (19 000 km) or at 12 months
²Replace engine oil and filter.
18,000 Miles (29 000 km) or at 18 months
²Replace engine oil and filter.
²Inspect brake linings.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
24,000 Miles (38 000 km) or at 24 months
²Replace engine oil and filter.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
30,000 Miles (48 000 km) or at 30 months
²Replace engine oil and filter.
²Replace engine air cleaner element.
²Replace spark plugs.
36,000 Miles (58 000 km) or at 36 months
²Replace engine oil and filter.
²Drain and refill transfer case fluid.
²Inspect brake linings
²Flush and replace engine coolant at 36 months,
regardless of mileage.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
42,000 Miles (67 000 km) or at 42 months
²Replace engine oil and filter.
48,000 Miles (77 000 km) or at 48 months
²Replace engine oil and filter.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Flush and replace engine coolant if not done at
36 months.
54,000 Miles (86 000 km) or at 54 months
²Replace engine oil and filter.
²Inspect brake linings.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
60,000 Miles (96 000 km) or at 60 months
²Replace engine oil and filter.
²Replace engine air cleaner element.
²Replace ignition cables.
²Replace spark plugs.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
66,000 Miles (106 000 km) or at 66 months
²Replace engine oil and filter.
72,000 Miles (115 000 km) or at 72 months
²Replace engine oil and filter.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Drain and refill transfer case fluid.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
²Inspect brake linings.
78,000 Miles (125 000 km) or at 78 months
²Replace engine oil and filter.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
84,000 Miles (134 000 km) or at 84 months
²Replace engine oil and filter.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
90,000 Miles (144 000 km) or at 90 months
²Replace engine oil and filter.
²Replace engine air cleaner element.
²Replace spark plugs.
²Inspect brake linings.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
96,000 Miles (154 000 km) or at 96 months
²Replace engine oil and filter.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
102,000 Miles (163 000 km) or at 104 months
²Replace engine oil and filter.
108,000 Miles (173 000 km) or at 110 months
²Replace engine oil and filter.
²Drain and refill transfer case fluid.
²Inspect brake linings.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
0 - 14 LUBRICATION & MAINTENANCEBR/BE
MAINTENANCE SCHEDULES (Continued)

²Inspect brake linings.
³Off-the-highway operation, trailer towing snow
plowing, prolonged operation with heavy loading,
especially in hot weather require the more frequent
transmission service indicated with an ³ in Schedule
ªBº. Perform these services if the vehicle is usually
operated under these conditions.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
DESCRIPTION - HEAVY DUTY ENGINE
(FEDERAL ONLY ± 2500 8.0L HD AND 3500
5.9L& 8.0L MODELS) MAINTENANCE
SCHEDULES
There are two maintenance schedules that show
proper service based on the conditions that the vehi-
cle is subjected to. Use the schedule that best
describes these conditions.
ScheduleªAº, lists all the scheduled maintenance
to be performed under normal operating conditions
for Heavy Duty vehicles.
ScheduleªBº, lists maintenance recommended for
Heavy Duty vehicles operated under the conditions
listed at the beginning of that schedule.
²Where time and mileage are listed, follow the
interval that occurs first.
At Each Stop For Fuel
²Check engine oil level, add as required.
²Check windshield washer solvent and add if
required.
²Clean windshield and wiper blades as required.
Once A Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect battery and clean and tighten terminals
as required.
²Check fluid levels of coolant reservoir, power
steering and transmission and add as needed.
²Check all lights and all other electrical items for
correct operation.
²Inspect and clean wiper blades. Replace if
required.
At Each Oil Change
²Inspect exhaust system.
²Inspect brake hoses.
²Adjust rear brakes.
²Rotate the tires at each oil change interval
shown on schedule ªAº (6,000 Miles) or every other
interval shown on schedule ªBº (6,000 Miles).
²Check engine coolant level, hoses, and clamps.
²Lubricate steering linkage.
EMISSION CONTROL SYSTEM MAINTENANCE
The scheduled emission maintenance listed inbold
typeon the Maintenance Schedules, must be done at
the mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
FLUID FILL LOCATIONS AND LUBRICATION
POINTS
The fluid fill/check locations and lubrication points
are located in each applicable group.
HEAVY DUTY SCHEDULE ªAº
6,000 miles (10 000 km) or at 6 months
²Change engine oil.
²Replace engine oil filter.
12,000 Miles (19 000 km) or at 12 months
²Change engine oil.
²Replace engine oil filter.
²Inspect engine air cleaner element, replace
as necessary (8.0L only).
18,000 Miles (29 000 km) or at 18 months
²Change engine oil.
²Replace engine oil filter.
²Inspect brake linings
²Inspect front wheel bearings. Clean and repack,
if required (4x4).
24,000 Miles (38 000 km) or at 24 months
²Change engine oil.
²Replace engine oil filter.
²Replace engine air cleaner element and air
pump filter.
²Clean and lubricate crankcase inlet air filter
(5.9L).
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
30,000 Miles (48 000 km) or at 30 months
²Change engine oil.
²Replace engine oil filter.
²Replace spark plugs.
36,000 Miles (58 000 km) or at 36 months
²Change engine oil.
²Replace engine oil filter.
BR/BELUBRICATION & MAINTENANCE 0 - 17
MAINTENANCE SCHEDULES (Continued)

99,000 Miles (156 000 km)
²Change engine oil.
²Replace engine oil filter.
²Lubricate tie rod ends every 3,000 miles (5 000
km).
²Inspect front wheel bearings (4x2).
102,000 Miles (163 000 km)
²Change engine oil.
²Replace engine oil filter.
²Lubricate tie rod ends every 3,000 miles (5 000
km).
²Inspect front wheel bearings (4x4).
105,000 Miles (168 000 km)
²Change engine oil.
²Replace engine oil filter.
²Lubricate tie rod ends every 3,000 miles (5 000
km).
108,000 Miles (173 000 km)
²Change engine oil.
²Replace engine oil filter.
²Inspect engine air cleaner element and air
pump filter, replace as necessary.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.³
²Drain and refill transfer case fluid (4x4).
²Change rear axle fluid.
²Change front axle fluid (4x4).
²Inspect brake linings.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) since last change.
²Lubricate tie rod ends every 3,000 miles (5 000
km).
²Inspect front wheel bearings (4x4).
²Inspect front wheel bearings (4x2).
*Requires Service Reminder Indicator Light. If so
equipped, these parts are to be replaced at the indi-
cated mileage or when the service reminder indicator
light remains on continuously with the key in the
ªONº position, whichever occurs first.
³Off-the-highway operation, trailer towing, snow
plowing, prolonged operation with heavy loading,
especially in hot weather require the more frequent
transmission service indicated witha³inSchedule
ªBº. Perform these services if you usually operate
your Ram Truck under these conditions.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
DESCRIPTION - MAINTENANCE SCHEDULES
Ð 24±VALVE CUMMINS TURBO DIESEL
There are two maintenance schedules that show
proper service for the vehicle.First is ScheduleªA.ºIt lists all the scheduled
maintenance to be performed under ªnormalº operat-
ing conditions.
Second is ScheduleªB.ºIt is a schedule for vehicles
that are operated under the conditions listed at the
beginning of that schedule.
Use the schedule that best describes the driving
conditions.
Where time and mileage are listed, follow the
interval that occurs first.
At Each Stop For Fuel
²Check engine oil level and add as required.
²Check windshield washer solvent and add if
required.
²Clean windshield and wiper blades as required.
²Drain water from fuel filter.
Once A Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect battery and clean and tighten terminals
as required.
²Check fluid levels of coolant reservoir, brake
master cylinder, power steering, and transmission.
Add fluid as required.
²Check all lights and all other electrical items for
correct operation.
²Check Filter Mindery. Replace air cleaner
element if necessary.
²Inspect and clean wiper blades. Replace if
required.
At Each Oil Change
²Inspect exhaust system.
²Inspect brake hoses.
²Adjust rear brakes.
²Rotate the tires at each oil change interval
shown at 7, 5000 miles (12 000 km) on schedule ªAº
or every other interval shown at 7,500 miles (12 000
km) on schedule ªBº.
²Check engine coolant level, hoses, and clamps.
²Lubricate steering linkage.
²Drain crankcase breather canister (if equipped).
EMISSION CONTROL SYSTEM MAINTENANCE
The scheduled emission maintenance listed inbold
typeon the Maintenance Schedules, must be done at
the mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
0 - 22 LUBRICATION & MAINTENANCEBR/BE
MAINTENANCE SCHEDULES (Continued)

FLUID FILL LOCATIONS AND LUBRICATION
POINTS
The fluid fill/check locations and lubrication points
are located in each applicable group.
SCHEDULE ªAº
7,500 Miles (12 000 km) or at 6 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
15,000 Miles (24 000 km) or at 12 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
22,500 Miles (36 000 km) or at 18 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect drive belts, replace as necessary.
²Inspect brake linings.
30,000 Miles (48 000 km) or at 24 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect fan hub.
²Inspect damper.
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
²Flush and replace engine coolant if not done at
36 months.
37,500 Miles (60 000 km) or at 30 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
45,000 Miles (72 000 km) or at 36 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect drive belts, replace as necessary.
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
²Drain and refill transfer case fluid.
²Inspect brake linings.
²Flush and replace engine coolant if not done at
24 months
52,500 Miles (84 000 km) or at 42 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
60,000 Miles (96 000 km) or at 48 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Inspect fan hub.
²Inspect damper.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
67,500 Miles (108 000 km) or at 54 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect drive belts, replace as necessary.
²Inspect brake linings.
75,000 Miles (120 000 km) or at 60 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
82,500 Miles (132 000 km) or at 66 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
90,000 Miles (144 000 km) or at 72 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
²Inspect drive belt, replace as required.
²Drain and refill automatic transmission fluid.
Replace filter and adjust bands.
²Drain and refill transfer case fluid.
²Inspect fan hub.
²Inspect damper.
²Inspect water pump weep hole for blockage.
²Replace fuel filter and clean water in fuel sen-
sor.
²Inspect front wheel bearings. Clean and repack,
if required (4x2).
²Inspect brake linings.
97,500 Miles (156 000 km) or at 78 months
²Change engine oil and filter.
²Drain crankcase breather canister (if equipped).
BR/BELUBRICATION & MAINTENANCE 0 - 23
MAINTENANCE SCHEDULES (Continued)

CORRECTED CASTER CHART-CAB CHASSIS
Caster
Correlation
Value
(inches)4x2 8800
lb. GVW
134.7 in.
wheel
base4x4 8800
lb. GVW
4x2 & 4x4
11000 lb.
GVW
134.7 &
138.7 in.
wheel
base4x2 & 4x4
11000 lb.
GVW 162.7
in. wheel
base
Caster61
deg.Caster61
deg.Caster61
deg.
þ5.00 4.27É 3.77É 3.81É
þ4.75 4.39É 3.89É 3.91É
þ4.50 4.51É 4.01É 4.01É
þ4.25 4.64É 4.14É 4.11É
þ4.00 4.76É 4.26É 4.21É
þ3.75 4.88É 4.38É 4.31É
þ3.50 5.00É 4.50É 4.41É
þ3.25 5.12É 4.62É 4.51É
þ3.00 5.25É 4.75É 4.61É
þ2.75 5.37É 4.87É 4.71É
þ2.50 5.49É 4.99É 4.81É
þ2.25 5.61É 5.11É 4.91É
þ2.00 5.74É 5.24É 5.01É
þ1.75 5.86É 5.36É 5.11É
þ1.50 5.98É 5.48É 5.21É
þ1.25 6.10É 5.60É 5.31É
þ1.00 6.23É 5.73É 5.41É
þ0.75 6.33É 5.83É 5.51É
þ0.50 6.47É 5.97É 5.61É
þ0.25 6.59É 6.09É 5.71É
0.00 6.71É 6.21É 5.81É
STANDARD PROCEDURES - ALIGNMENT
LINK/COIL SUSPENSION
Before each alignment reading the vehicle should
be jounced (rear first, then front). Grasp each
bumper at the center and jounce the vehicle up and
down several times. Always release the bumper in
the down position.Set the front end alignment to
specifications while the vehicle is in its NOR-
MALLY LOADED CONDITION.
CAMBER:The wheel camber angle is preset and
is not adjustable.
CASTER:Check the caster of the front axle for
correct angle. Be sure the axle is not bent or twisted.Road test the vehicle and make left and right turn.
Observe the steering wheel return-to-center position.
Low caster will cause poor steering wheel returnabil-
ity.
Caster can be adjusted by rotating the cams on the
lower suspension arm (Fig. 5). (Refer to 2 - SUSPEN-
SION/WHEEL ALIGNMENT - STANDARD PROCE-
DURE).
TOE POSITION:The wheel toe position adjust-
ment should be the final adjustment.
(1) Start the engine and turn wheels both ways
before straightening the wheels. Center and Secure
the steering wheel and turn off engine.
(2) Loosen the adjustment sleeve clamp bolts.
(3) Adjust the right wheel toe position with the
drag link. Turn the sleeve until the right wheel is at
the correct TOE-IN position. Position clamp bolts to
their original position and tighten to specifications.
Make sure the toe setting does not change dur-
ing clamp tightening.
(4) Adjust left wheel toe position with tie rod at
left knuckle. Turn the sleeve until the left wheel is at
the correct TOE-IN position. Position clamp bolts to
their original position and tighten to specifications.
Make sure the toe setting does not change dur-
ing clamp tightening.
(5) Verify the right toe setting.
Fig. 5 Adjustment Cam
1 - ADJUSTMENT CAM
2 - AXLE BRACKET
3 - BRACKET REINFORCEMENT
4 - LOWER SUSPENSION ARM
BR/BEWHEEL ALIGNMENT 2 - 5
WHEEL ALIGNMENT (Continued)

DRIVELINE VIBRATION
Drive Condition Possible Cause Correction
Propeller Shaft Noise 1) Undercoating or other foreign
material on shaft.1) Clean exterior of shaft and wash
with solvent.
2) Loose U-joint clamp screws. 2) Install new clamps and screws
and tighten to proper torque.
3) Loose or bent U-joint yoke or
excessive runout.3) Install new yoke.
4) Incorrect driveline angularity. 4) Measure and correct driveline
angles.
5) Rear spring center bolt not in
seat.5) Loosen spring u-bolts and seat
center bolt.
6) Worn U-joint bearings. 6) Install new U-joint.
7) Propeller shaft damaged or out
of balance.7) Installl new propeller shaft.
8) Broken rear spring. 8) Install new rear spring.
9) Excessive runout or unbalanced
condition.9) Re-index propeller shaft, test,
and evaluate.
10) Excessive drive pinion gear
shaft runout.10) Re-index propeller shaft and
evaluate.
11) Excessive axle yoke deflection. 11) Inspect and replace yoke if
necessary.
12) Excessive transfer case runout. 12) Inspect and repair as necessary.
Universal Joint Noise 1) Loose U-joint clamp screws. 1) Install new clamps and screws
and tighten to proper torque.
2) Lack of lubrication. 2) Replace as U-joints as
necessary.
BALANCE
NOTE: Removing and re-indexing the propeller
shaft 180É relative to the yoke may eliminate some
vibrations.
If propeller shaft is suspected of being unbalanced,
it can be verified with the following procedure:
(1) Raise the vehicle.
(2) Clean all the foreign material from the propel-
ler shaft and the universal joints.
(3) Inspect the propeller shaft for missing balance
weights, broken welds, and bent areas.If the pro-
peller shaft is bent, it must be replaced.
(4) Inspect the universal joints to ensure that they
are not worn, are properly installed, and are cor-
rectly aligned with the shaft.
(5) Check the universal joint clamp screws torque.
(6) Remove the wheels and tires. Install the wheel
lug nuts to retain the brake drums or rotors.
(7) Mark and number the shaft six inches from the
yoke end at four positions 90É apart.(8) Run and accelerate the vehicle until vibration
occurs. Note the intensity and speed the vibration
occurred. Stop the engine.
(9) Install a screw clamp at position 1 (Fig. 6).
(10) 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.
(11) If there is no difference in vibration at the
other positions, the source of the vibration may not
be propeller shaft.
(12) If the vibration decreased, install a second
clamp (Fig. 7) and repeat the test.
(13) If the additional clamp causes an additional
vibration, separate the clamps (1/2 inch above and
below the mark). Repeat the vibration test (Fig. 8).
(14) 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.
3 - 4 PROPELLER SHAFTBR/BE
PROPELLER SHAFT (Continued)

cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side-gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by:
²Damaged drive shaft.²Missing drive shaft balance weight(s).
²Worn or out of balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front end components
or engine/transmission mounts. These components
can contribute to what appears to be a rear end
vibration. Do not overlook engine accessories, brack-
ets and drive belts.
All driveline components should be examined
before starting any repair.
(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND
TESTING)
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted
into gear (or the clutch engaged) can be caused by:
²High engine idle speed.
²Transmission shift operation.
²Loose engine/transmission/transfer case mounts.
²Worn U-joints.
²Loose spring mounts.
²Loose pinion gear nut and yoke.
²Excessive ring gear backlash.
²Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-
mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.
3 - 14 FRONT AXLE - 216FBIBR/BE
FRONT AXLE - 216FBI (Continued)

OPERATION
The shift motor receives a vacuum signal from the
switch mounted on the transfer case when the vehi-
cle operator wants to switch from two wheel drive
mode to four wheel drive mode, or vice versa. When
this signal is received, the shift motor begins to move
the shift fork and collar within the axle housing. In
the four wheel drive mode, the shift collar connects
the axle intermediate shaft to the axle shaft to sup-
ply engine power to both front wheels. In two wheel
drive mode, the shift collar is disengaged from the
intermediate shaft and the intermediate shaft is
allowed to free-spin. When the two shafts are disen-
gaged, the load on the engine is reduced, thereby pro-
viding better fuel economy and road handling.
Fig. 27 Vacuum Control System
1 - CHECK VALVE
2 - CONTROL SWITCH ON TRANSFER CASE
3 - AIR VENT FILTER
4 - AXLE SHIFT MOTOR
5 - INDICATOR SWITCH
3 - 30 FRONT AXLE - 216FBIBR/BE
AXLE VACUUM MOTOR (Continued)

cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side-gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by:
²Damaged drive shaft.²Missing drive shaft balance weight(s).
²Worn or out of balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front end components
or engine/transmission mounts. These components
can contribute to what appears to be a rear end
vibration. Do not overlook engine accessories, brack-
ets and drive belts.
All driveline components should be examined
before starting any repair.
(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND
TESTING)
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted
into gear (or the clutch engaged) can be caused by:
²High engine idle speed.
²Transmission shift operation.
²Loose engine/transmission/transfer case mounts.
²Worn U-joints.
²Loose spring mounts.
²Loose pinion gear nut and yoke.
²Excessive ring gear backlash.
²Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-
mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.
BR/BEFRONT AXLE - 248FBI 3 - 47
FRONT AXLE - 248FBI (Continued)