Diagnosis will be much easier once you have identified
a vibration as first-order of driveline rotation during the road test. Next
identify the exact area of the vibration and take proper action.
In most cases, vibration may be reproduced in the stall. In the stall
the vibration may be better or worse than that experienced during the road
test.
The objective is to reduce the vibration to the lowest point possible
in the stall, then evaluate the results during a road test. Many times, a
vibration you were only able to reduce drastically in the stall will be
completely eliminated on the road.
The cause of first-order drive line vibration is usually excessive runout
or an imbalanced component.
The following procedure offers a systematic process of elimination in
order to determine which component is at fault:
- Raise the vehicle to curb height. Support the vehicle on a hoist
or heavy stands. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Remove the rear tire/wheel assemblies. Refer to
Tire and Wheel Removal and Installation
in Tires
and Wheels.
- Remove the brake drums. Refer to
Brake Drum Replacement
in Drum Brakes.
- Inspect the propeller shaft. The propeller shaft should be free
of undercoating before continuing.
- Inspect the propeller shaft or U-Joint for any obvious dents or
damage. Dents or damage will contribute to first-order driveline vibrations.
- Start the engine.
- Place the transmission in gear.
- Run the vehicle up to the speed at which the vibration was most
severe. Do not step on the brake while the brake drums are removed.
- Record whether the vibration was present, and at what speed.
- If the vibration is not present, refer to First-Order Driving
Vibration Testing (Torque Sensitive) in the Road Testing Diagnosis.
- If the vibration is present, determine which end of the driveshaft
is vibrating the most. Hold your hand against the pinion nose and the transmission
tailshaft, or hold an EVA vibration sensor up to each component.
- If the vehicle is equipped with a two-piece propeller shaft, inspect
the center support bearing for vibration.
- If the transmission tail is vibrating, touch the transmission
crossmember under the transmission mount. If there is no vibration on the
crossmember, then the transmission mount is working properly.
- Remember which end of the driveshaft is the worst, and how severe
the vibration is. The inspection will be a reference by which to judge future
progress.
Do not fill the propeller shaft with foam, oil, or any other substance
in order to correct a vibration. Filling the propeller shaft is only effective
in reducing an unrelated condition called Torsional Rattle. Filling the
propeller shaft should only be done in strict adherence to the procedure
outlined in corporate bulletins that address Torsional Rattle. Failure to
follow the correct procedure will induce a vibration and/or affect the structural
integrity of the propeller shaft. The propeller shaft will then have to
be replaced.
Propeller Shaft Runout
A propeller shaft or pinion (companion) flange with excessive runout
causes first-order driveline vibrations. Use the following procedure in order
to measure the runout of the propeller shaft:
• | Remove excess corrosion of the propeller shaft surface before
inspecting the runout. |
• | Inspect for damage and dents. |
• | Replace dented propeller shafts. |
• | Remove any undercoating from the propeller shaft before proceeding. |
• | Refer to Measuring Propeller Shaft Runout, below, for the measurement
procedure that applies to the following shaft assemblies: |
The splined end of a propeller shaft is critical to the smooth operation
of a two-piece propeller shaft. When inspecting stub-shaft runout, ensure
that the dial indicator readings are accurate.
The front or the auxiliary propeller shaft on 4-wheel (4WD) drive models
may sometimes cause vibration. If a first-order vibration is present only
when the vehicle is in 4WD, remove the auxiliary propeller shaft and re-evaluate
the vibration. If the vibration goes away, the auxiliary shaft is most likely
at fault. Investigate the condition of the auxiliary shaft.
Measuring Propeller Shaft Runout
Tools Required
• | J 7872 Magnetic
Base Dial Indicator Set |
Important: When you replace a propeller shaft, inspect the new shaft for runout.
Inspect the pinion flange runout if the replacement shaft runout is also out
of tolerance.
Specifications
|
Propshaft
| Front Runout
| Center Runout
| Rear Runout
| Stub Shaft Runout
|
One-Piece
| Measure
| Measure
| Measure
| --
|
Two-Piece
| Measure
| Measure
| Measure
| --
|
Three-Piece
| Measure
| Measure
| Measure
| --
|
Measuring Pinion Flange Runout
Tools Required
- Place the vehicle on a suitable hoist. Refer to
Lifting and Jacking the Vehicle
in General Information.
Allow the wheels to rotate freely.
- Remove the propeller shaft from the pinion flange.
- Install the J 35819
.
Important: The dial indicator will have inverted readings. You are measuring the
inside diameter of the flange; you are not measuring the outside diameter.
The highest reading on the dial indicator is the low spot. The lowest reading
is the high spot.
- Rotate the pinion shaft 360 degrees and zero the dial indicator
on the low spot.
- Rotate the pinion flange again and record the total runout.
- If the pinion flange runout is 0.15 mm (0.006 in)
or less, remove the pinion flange balance weight.
- If the pinion flange runout is greater than 0.15 mm (0.006 in)
but not less than 0.28 mm (0.011 in), and the runout compensation
weight is at or near the low spot, no further action is necessary. If the
runout compensation weight is not at or near the low spot, remove the weight.
- If the pinion flange runout is greater than 0.28 mm (0.011 in)
but not greater than 0.38 mm (0.015 in), and the balance weight
is at or near the low point, no further action is necessary. If the runout
compensation weight is not at or near the low spot, remove the weight and
re-index the pinion flange until the runout is 0.25 mm (0.010 in)
or less.
- Replace the pinion shaft when the runout is 0.25 mm (0.010 in)
or less. Then, recheck the runout. Service replacement flanges do not have
balance weights.
Helpful Hints
• | If a J 35819
is
not available, measure the pinion runout as close as possible to the pinion
flange. |
• | If necessary, add compensation
weights on the face of the pinion flange dust slinger. These weights are
tack-welded onto the slinger. You may remove the weights with a die-grinder. |
• | Carefully remove the spot weld at either end of the weight. |
• | Do not remove the weight unless you have inspected the pinion
flange runout and the procedure calls for weight removal. |
• | Do not remove any weights on the outboard edge of the dust slinger.
These weights are present in order to balance internal axle components. The
weights are not related to the pinion flange runout. |
• | If a J 35819
is
not available, inspect the propeller shaft runout as near as possible to
the flange. Rotate the shaft 180 degrees in the pinion flange. Reinstall
the shaft. Inspect the measurement at the same location. |
| A large difference in the runout, greater than 0.38 mm (0.015 in),
may indicate that the flange is out of tolerance. If the runout does not change
at all, the flange is OK. |
Balanced Axles
Beginning in the early 1990's, the manufacturer began system balancing
rear axles. During the build process, these axle assemblies were spun with
a slave fixture. A balance weight was attached to the outboard edge of
the companion flange dust slinger. A system-balanced rear axle companion
flange differs from a non-balanced flange. You must diagnose and service
this flange in a unique way.
Some pinion flange assemblies have a U-shaped deflector designed to
hold a system balance weight on the outside diameter.
Other pinion flange assemblies have a runout compensation weight on
the face of the deflector. The pinion flange assemblies that are system balanced
do not use runout compensation weights.
Measuring the runout on a system-balanced companion flange is very straight-forward.
A balanced flange that is good will have a measured runout between 0.00-0.38 mm
(0.00-0.015 in). If a balanced flange has more than 0.38 mm
(0.015 in) runout, replace the flange or reindex the flange 180 degrees
on the pinion. If you replace or reindex a balanced flange, you must system
balance the rear axle again.
Correcting Vibration at the Pinion Nose
Most first-order driveline vibrations originate at the pinion nose end
of the driveshaft. Ensure that the vibrations are at a minimum at this location
in order to achieve acceptable results. Reduce the runout of the components
to a minimum. Balance the driveline as a system when necessary.
- Measure the runout of the propeller shaft and inspect the tolerance.
- If the tolerance is excessive, mark the position of the shaft
for future reference and rotate the shaft 180 degrees.
- Reinstall the shaft and reinspect the runout. Inspect the level
of vibration in order to determine if the vibration is lower or corrected.
- If the runout is still excessive, or if the vibration is still
present, refer to Measuring Pinion Flange Runout. Replace the pinion flange
or re-index the flange 180 degrees if the pinion flange runout exceeds
the tolerance.
Remove and reinstall the pinion flange only once on axles utilizing
a crush type sleeve. Replace the sleeve with a new sleeve if the sleeve is
crushed. Removing the sleeve requires removal of the ring and pinion set.
Replace flanges with excessive runout. Regardless of the method used, measure
the pinion flange runout in order to ensure that the flange is within tolerance.
- Reinspect the propeller shaft runout if the vibration is present
after the pinion flange runout is corrected. If the propeller shaft runout
is still excessive, correct the runout before doing a driveline system
balance. Either replace the shaft with a shaft that is within tolerance
or sublet the shaft to a reputable independent for straightening and re-balance.
Ensure that the new or rebuilt shaft is within runout tolerance before
continuing.
- Once the propeller shaft and pinion flange are within runout tolerances,
inspect to see if the vibration is still present. If the level of the vibration
is still unacceptable, perform a driveline system balance procedure.
Correcting Vibration at the Transmission Tailshaft
First-order driveline vibrations that originate at the transmission
end of the propeller shaft are rare. If the tailshaft of the transmission
is vibrating, inspect the tailshaft housing bushing for wear or damage.
A leaky transmission tailshaft oil seal indicates bushing problems.
Feel for vibration at the crossmember underneath the transmission mount.
If there is no vibration, the transmission mount is functioning properly by
isolating the vibration from the structure of the vehicle. The transmission
mount is therefore probably not the cause of the vibration.
Use the following procedure if you can feel vibration on the crossmember
and the tailshaft bushing, and if the transmission output is normal:
- Measure the propeller
shaft runout. If the runout is excessive, replace the shaft with one that
has acceptable runout. Alternatively, sublet the shaft to a reputable independent
service shop in order to have the shaft rebalanced and the runout corrected.
- Test drive the vehicle. If the vibration is still unacceptable,
balance the shaft on the vehicle. Refer to Rear Driveline System Balance.
Correcting Vibration at the Center Support Bearing
These guidelines apply to the two-piece propeller shaft only. First-order
driveline vibrations that occur mainly at the center support bearing are usually
the result of excessive runout at the stub (splined) shaft.
Unlike other first-order driveline vibrations, these vibrations can
appear at unusually low speeds of 40 km/h (25 mph) and up.
Perform the following procedure in order to correct this type of vibration:
- Mark the position of the rear propeller shaft at both ends for
proper reassembly.
- Remove the rear propeller shaft from the vehicle.
Correcting the stub shaft/spline runout will usually eliminate the vibration.
If some residual vibration is still present, perform a road test on the vehicle.
Determine if an on-vehicle system balance of the driveline is necessary.
Driveline System Balance without the Electronic Vibration Analyzer
(EVA)
The following procedure is designed to fine-tune the balance of the
propeller shaft while it is mounted in the vehicle. This procedure will also
correct residual imbalance of the remaining driveline components.
Prior to balancing the driveline system, verify that the propeller shaft
and the pinion flange runout are within specification.
Do not overheat the engine when performing this procedure.
- Raise the vehicle to curb height. Support the vehicle on a hoist
or on safety stands. Do not allow the axle to hang. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Remove the rear tire/wheel assemblies. Refer to
Tire and Wheel Removal and Installation
in Tires
and Wheels.
- Remove the brake drums. Refer to
Brake Drum Replacement
in Drum Brakes.
- Determine which end of the propeller shaft has the most vibration
in order to identify where to begin installing the hose clamps.
The following procedure uses a trial and error method of determining
where to place the hose clamps on the shaft. Use the following tips in order
to help locate the clamps:
- Because the imbalance may be related to propeller shaft runout,
begin installing the clamps at the low point of the propeller shaft runout.
- When the plant workers balance the propeller shaft, they use weights
in graduated increments: 1/16 oz, 1/8 oz, etc. If the stock
weight is too light or too heavy, place the hose clamp either directly
in line with or opposite to the stock weight.
The last method involves running the vehicle at a speed which the vibration
is felt.
- Carefully hold a piece of chalk up to the very end of the propeller
shaft. Barely touch the chalk to the shaft.
- Shut the engine OFF in order to stop the propeller shaft from
rotating. Do not step on the brake pedal. Do not put the transmission in PARK.
- Inspect the chalk mark.
If you performed the above procedure correctly, the chalk mark will
indicate the heavy spot on the shaft. The heavy spot will deflect downward
and touch the chalk. If the chalk mark circles the entire shaft, touch
the chalk more gently to the shaft. Ensure that the chalk touches only
the heavy spot. Once the heavy spot is located, place the hose clamp 180 degrees
opposite to the chalk mark. Perform the following steps:
• | If the vibration did not change at all or if the vibration becomes
worse, then 1 clamp is either too light or too heavy. Repeat the procedure
using the 2 clamps together. |
• | If the previous step did not correct the problem, repeat the procedure
using the 2 clamps separated in order to reduce the spinning weight. |
Continue the trial and error procedure using different weights in different
locations until you achieve the best balance. If more that 3 clamps
aligned in the same position are required, replace the propeller shaft.
If you are able to reduce the vibration in the stall, but are unable
to eliminate the vibration completely, perform a road test on the vehicle.
A slight vibration noticeable in the stall may not be noticeable on the
road.
Driveline System Balance with Electronic Vibration Analyzer (EVA)
In order to pinpoint the source, you must reproduce the vibration in
the service stall. Determine which component is vibrating the most using the
EVA. Perform the following steps:
- Support the vehicle on a suitable hoist or on safety stands. Ensure
that the rear of the rear axle is at curb height. Do not allow the axle to
hang. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Remove the rear tire/wheel assemblies. Refer to
Tire and Wheel Removal and Installation
in Tires
and Wheels.
- Remove the brake drums. Refer to
Brake Drum Replacement
in Drum Brakes.
- Ensure that the propeller shaft is free of undercoating. Check
for dents or damage to the propeller shaft or U-Joint.
- Start the engine.
- Place the transmission in gear.
- Run the engine at the vehicle speed at which the vibration is
occurring.
Caution: Do not run the vehicle higher than 89 km/h (55 mph). Stay
clear of the universal joints and the balance weight area in order to avoid
personal injury. Do not run the vehicle on the hoist for extended periods
of time. Running the vehicle on the hoist for extended periods of time may
cause the engine or the transmission to overheat.
Determine which end of the propeller shaft is vibrating the most. Hold
the EVA's sensor against the pinion nose and the transmission tailshaft assembly.
The higher the amplitude reading, the greater the vibration.
• | If the vehicle has a two-piece or three-piece propeller shaft,
inspect the center support bearing. |
• | If the transmission tailshaft vibrates, inspect the transmission
crossmember under the transmission mount. The vibration should not be present
if the mount is functioning correctly. |
Strobe Balance Testing with the Electronic Vibration Analyzer (EVA)
Ensure that the runout of the various driveline components are within
specifications. If the runouts are within specifications, strobe balance the
driveline. The EVA is able to simplify the balancing process, using the
following procedure:
- Use the EVA in order to determine which end of the propeller shaft
has the most vibration.
If the shaft will not balance using 2 weights, place a third
weight on the light spot. Split the first 2 weights in order to produce
a total weight between 2 and 3 weights.
If 3 weights fail to balance the driveline, replace the propeller
shaft.
When the propeller shaft balances, road test the vehicle in order to
verify that the vibration is eliminated.
Propeller Shaft Balance Weights
When using clamps in order to balance a propeller shaft with the total
weight method, the correction weight required will often be a fraction or
a multiple of one hose clamp. Use the following phasing procedure with
2 hose clamps in order to accurately place any required amount 0-2 weights
(0.0-2.0 total wieghts).
|
(1) | Balance Location |
(2) | Clamps Together |
- Ensure that the clamps are located with even spaces on either side of
the light spot, or 180 degrees opposite the heavy spot.
The table containing the weight amounts in terms of the total weight
and the included angle (spread) between the clamps is in specifications. Refer
to Specifications.
- If the vibration does not change at all or gets worse, then 1 clamp
is too light or too heavy. Repeat the procedure using the 2 clamps
together.
- If the previous step did not correct the problem, repeat the procedure
using the 2 clamps separated in order to reduce the spinning weight.
- Continue the trial and error procedure using different weights
in different locations until you achieve the best balance.
- If more than 3 clamps aligned in the same position are
required, replace the propeller shaft.
- If you are able to reduce the vibration in the stall, but are
unable to eliminate the vibration completely, road test the vehicle. A slight
vibration noticeable in the stall may not be noticeable on the road.
First-Order Driveline Vibration Analysis (Torque Sensitive)
If the following conditions are true, the internal rear axle components
are the probable cause of the vibration:
• | If the vehicle has a vibration that is equal to first-order driveline
rotation, and the vibration is not present when testing the vehicle in the
stall |
• | If you were able to correct the vibration in the stall, but the
vibration returned during the road test |
Internal rear axle vibrations may be aggravated by the load of the vehicle
working against the ring and pinion gear seat.
Since the propeller shaft and the pinion gear are bolted together through
the pinion flange, the propeller shaft and the pinion gear operate at the
same speed. Vibration in the pinion gear will therefore have the same frequency
and symptoms as the propeller shaft.
In order to isolate the vibration to the pinion gear, use the following
procedure:
- Raise the vehicle to curb height. Support the vehicle on a hoist
or on safety stands. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Remove the tire/wheel assemblies. Refer to
Tire and Wheel Removal and Installation
in Tires
and Wheels.
- Remove the brake drums. Refer to
Brake Drum Replacement
in Drum Brakes.
- Touch the pinion nose or hold the EVA vibration sensor up to the
pinion nose.
- With the aid of another technician, accelerate and decelerate
the vehicle through the speed range at which the vibration was noticed during
the road test.
Example
• | If the vibration was originally noticed at 88 km/h (55 mph),
accelerate from 72 km/h (45 mph) to 107 km/h (65 mph).
Then decelerate from 107 km/h (65 mph) back to 72 km/h
(45 mph). |
• | Repeat the above step and remember whether or not the pinion nose
vibrates under load during acceleration and/or deceleration. |
If the vibration does not occur during the above procedure, install
the brake drums and the tire/wheel assemblies, adding additional load on the
system. Then repeat the above test.
Ensure that both axle shafts rotate at the same speed. The differential
may mask a vibration when one tire is spinning faster than the other tire.
Adjust the brakes in order to correct unequal tire rotation speed.
If you are unable to reproduce the vibration in the stall, apply the
brake lightly in order to load the system further. Maintain the vehicle speed
at which the vibration was noticed. Do not overheat the brakes.
If the pinion nose vibrates under acceleration and/or deceleration,
and the other driveline components are eliminated as the cause of the vibration,
then one of the following conditions may cause the vibration:
• | A high spot on the pinion gear |
• | A cocked pinion bearing |
• | An improper axle housing bore |
Anything that effects the pinion gear and how the pinion gear contacts
the rotating ring gear may contribute to a first-order, torque-sensitive driveline
vibration. The only way to correct the condition is to replace the faulty
components. In most cases, you must replace the ring and pinion gear set
and the related bearings. In some cases, you must replace the axle housing.
Complete a close-up visual inspection for damage or unusual wear in order
to measure or identify the specific faulty component.
It is possible to isolate an internal axle vibration. Install a known
good axle assembly from a stock unit. Verify that the known good axle assembly
does not have a vibration problem.
Once you correct the internal axle problem, road test the vehicle. Inspect
the vehicle for vibration. Balance the driveline, as necessary, in order to
eliminate any remaining vibration.