Important: If you have not reviewed the Diagnostic Starting Point - Vibration
Diagnosis and completed the Vibration Analysis Tables as indicated, refer
to
Diagnostic Starting Point - Vibration Diagnosis and Correction
BEFORE proceeding.
The diagnostic information contained in this Diagnostic Aids section
will help you determine the correct course of action to take for the following
four main conditions. Refer to the appropriate condition following this list:
| • | Vibration NOT Duplicated or Intermittent Duplication |
| • | Vibration Duplicated - Difficult to Identify or Isolate
Component |
| • | Vibration Duplicated - Difficult to Balance or Isolate Component |
| • | Vibration Duplicated - Appears to be a Design Inherent Condition |
Vibration NOT Duplicated or Intermittent Duplication
If you have not been able to duplicate the vibration concern or have
only been able to duplicate the concern intermittently, review the following
information.
Most vibration concerns that cannot be duplicated are due to either
specific conditions that are not present during the duplicating attempts,
or due to not following the procedures designed to duplicate concerns properly
and in the sequence indicated.
Specific Conditions can Affect the Condition
Most attempts to duplicate a vibration concern are made after the vehicle
has been driven to the dealership and perhaps even sat inside the building
for a time. The opposite could also occur; perhaps the vehicle has sat out
in the cold for a time and fails to reach full operating temperatures during
attempts to duplicate the concern. The selection of roadways used to perform
the vibration duplication procedures is likely to be in the near vicinity
of the dealership. The vehicle is most likely empty of any payloads and usually
not bearing any kind of trailer.
Caution: Do NOT attempt to duplicate a vibration concern with specific conditions
indicated by the customer which would disobey local laws or ordinances, or
which could cause damage to the vehicle or be dangerous and possibly cause
physical injury or death, such as over-loading a vehicle, or driving at excessive
vehicle speeds.
Important: If the information you gained from the customer indicates that one or
more of the specific conditions listed applies to their concern, attempt to
duplicate the vibration concern again, while carefully recreating the EXACT
conditions necessary, with the exception of excessive speed, over-loading
the vehicle or towing a trailer. You are responsible to make sure that the
vehicle operates normally 'as-designed' and under 'normal operating conditions'
ONLY.
Consider the following conditions which may not have been present while
attempts were made to duplicate the vibration concern. Attempt to obtain more
specific information from the customer as to the EXACT conditions that are
present when they experience the vibration which they are concerned about,
then attempt to duplicate the vibration concern again while recreating the
EXACT conditions necessary, except those which pose a safety concern or are
outside the boundaries of normal operating conditions.
Temperature, Ground-Out, Accessory Load
| | Tires which have sat and been cool for a time can develop flat spots. |
| • | Irregular Wear on Tire Treads |
| | Tires which have sat and been cool for a time will be stiffer and any
irregular wear conditions will be more noticeable than they will be once the
tires have warmed and softened. |
| • | Exhaust System 'Growth' |
| | Exhaust systems may exhibit a ground-out condition when cool which goes
away once the system is fully warmed-up. The opposite may be true that the
exhaust system is fine when cool but a ground-out condition occurs once the
system reaches operating temperatures. [Exhaust systems can 'grow' by 2½
to 5 cm (1 to 2 in) when hot.] |
| • | Engine-Driven Accessory Noises |
| - | An engine accessory drive belt (or belts) could exhibit a whipping condition
if the belt is deteriorating and deposits are building up on the underside
of the belt. |
| - | Loose Mounting Brackets or Component Ground-Out |
| - | Engine-driven accessories such as a generator, a power steering pump
or an air conditioning compressor could exhibit noise conditions due to either
loose mounting brackets or due to related components of the system in a ground-out
condition during certain operation of that accessory system. |
| - | These accessories could exhibit noise conditions when cool which go
away once they are fully warmed-up, or the opposite may be true. |
| - | Load on an Accessory Component |
| - | These accessories could exhibit a noise condition while under a heavy
load -- perhaps when combined with a cool or fully warmed-up condition. |
| - | Bent or Misaligned Pulley(s) |
| - | Bent or mis-aligned pulley(s) in one or more engine-driven accessory
systems could contribute to a noise or vibration condition. |
| - | Fluid Level in Accessory System(s) |
| - | These accessories could exhibit a noise condition due to an abnormal
amount of fluid contained in the system of which the accessory is a part. |
| • | An improper power steering fluid level could produce noises in
the power steering system. |
| • | An improper air conditioning refrigerant level or an excessive
amount of refrigerant oil could produce noises or possibly vibrations in the
air conditioning system. |
| - | Incorrect Fluid Type in Accessory System(s) |
| - | These accessories could exhibit a noise condition due to the incorrect
type of fluid contained in the system of which the accessory is a part. |
Vehicle Payload
| | The vehicle may have been empty during attempts to duplicate the vibration
concern, while the customer may actually experience the vibration concern
while the vehicle is carrying a large payload. |
| | The customer may experience the vibration concern only while towing
a trailer. |
Roadway Selection
The customer may only experience the vibration on a particular roadway.
Perhaps the roadway is overly crowned or is very bumpy or rough.
Vibration Duplicated - Difficult to Identify or Isolate Component
Aftermarket Add-On Accessories
Aftermarket accessories which have been added to the vehicle can actually
transmit and magnify INHERENT component rotational frequencies, if the accessories
were not installed correctly.
An accessory should be installed in such a way that it is isolated from
becoming a possible transfer path into the rest of the vehicle. For example,
if a set of running boards has been installed improperly and they are sensitive
to a particular frequency of a rotating component, the running boards could
begin to respond to the frequency and actually create a disturbance once
the amplitude of the frequency reaches a high enough point (probably at a
higher vehicle speed).
Vibration Duplicated - Difficult to Balance or Isolate Component
If you have duplicated the vibration concern but have had difficulty
in balancing a component or isolating a component, refer to the following
information.
Most vibration concerns are corrected or eliminated through correcting
excessive runout of a component, correcting balance of a component or isolating
a component which has come into abnormal contact with another object/component.
Components which can generate a lot of energy and are experiencing excessive
runout, imbalance or ground-out can produce a vibration with a strong enough
amplitude that the vibration can transmit to components which are closely
related. This type of a condition is usually related to and sensitive to
torque-load. The most likely system that could exhibit this type of a condition
is the driveline.
Driveline Torque-Load Conditions
An axle differential that has internal problems such as excessive runout
of components, misalignment of components, imbalance, etc., can produce vibration
concerns which may be transmitted into the propeller shafts.
This sort of a vibration occurrence can increase or decrease in severity
based primarily upon torque-load, but can also be affected by cold or hot
conditions.
The propeller shaft and other related components may or may not pass
inspections for wear or damage, runout, alignment, etc., depending upon whether
there is only one vibration source or more than one.
Difficult to System Balance the Driveline
If after following the Vibration Analysis - Driveline Table you
were instructed to system balance the driveline and you experienced difficulty
in doing so while CAREFULLY following the procedures indicated (the EVA strobe
readings seem to keep changing), then the axle differential to which the
propeller shaft is attached should be suspected to have internal problems
which are being transmitted to the propeller shaft. Refer to A Diagnostic Starting Point - Rear Drive Axle
in Rear Drive
Axle, for internal axle diagnostics.
Vibration Duplicated - Appears to be a Design Inherent Condition
Check Service Bulletins
If BOTH of the following statements are TRUE, then check service bulletins
for the condition identified. If the condition has already been identified
and investigated prior to this vehicle, and has been determined to be something
that is not truly design-inherent or that perhaps is not design-intent, there
will likely be adjustments or corrections identified which will address the
condition.
- You CAREFULLY followed the steps indicated through reviewing the
Diagnostic Starting Point - Vibration Diagnosis and completing the Vibration
Analysis Tables identified and you have duplicated the vibration concern.
- You have come to the conclusion through comparison with a very
equally-equipped, same model year and type, KNOWN GOOD vehicle that the customer's
concern is a condition inherent to the design of the vehicle.
