Vibration - Drivetrain: Diagnosis Chevrolet TrailBlazer I

VIBRATION DIAGNOSIS & CORRECTION

Note. The following steps must be completed before using the analysis tables or the symptom tables.

1. See «VIBRATION ANALYSIS - ROAD TESTING»(ref-166336-S29544812532004091700000) before using the other Vibration Analysis tables or the Symptom tables in order to effectively diagnose the customer's concern. The use of Vibration Analysis and Road Testing will first provide duplication of virtually any vibration concern and then identify the correct procedure for diagnosing the area of concern which has been duplicated.
2. Review the following Vibration Diagnostic Process.
3. Review the general descriptions to familiarize yourself with vibration theory and terminology, the Electronic Vibration Analyzer (EVA) 2 (J-38792-A), and the Vibrate Software (J-38792-VS). Reviewing this information will help you determine whether the condition described by the customer is a potential operating characteristic or not. Refer to the following: See «VIBRATION THEORY & TERMINOLOGY»(ref-166336-S40612508342004091700000) under DESCRIPTION & OPERATION. See «ELECTRONIC VIBRATION ANALYZER (EVA)»(ref-166336-S37061621232004092000000) under DESCRIPTION & OPERATION. See «VIBRATE SOFTWARE»(ref-166336-S01076539142004092000000) under DESCRIPTION & OPERATION. See «REED TACHOMETER»(ref-166336-S12839339472004092000000) under DESCRIPTION & OPERATION.

Vibration Diagnostic Process

Note. Using the following steps of the vibration diagnostic process will help you to effectively narrow-down and pinpoint the search for the specific source of a vibration concern and to arrive at an accurate repair.

1. Gather specific information on the customer's vibration concern.
2. Perform the road testing steps in sequence as identified in «VIBRATION ANALYSIS - ROAD TESTING»(ref-166336-S29544812532004091700000) in order to duplicate the customer's concern and evaluate the symptoms of the concern under changing conditions. Observe what the vibration feels like and what it sounds like. Observe when the symptoms first appear, when they change, and when they cease.
3. Determine if the customer's vibration concern is truly an abnormal condition or something that is potentially an operating characteristic of the vehicle.
4. Systematically eliminate or "rule-out" possible vehicle systems.
5. Focus diagnostic efforts on the remaining vehicle system and systematically eliminate or "rule-out" possible components of that system.
6. Make a repair on the remaining component, or components, which have not been eliminated systematically, and must therefore be the cause of the vibration.
7. Verify that the customer's concern has been eliminated or at least brought to an acceptable level.
8. Again perform the road testing steps in sequence as identified in Vibration Analysis and Road Testing in order to verify that the vehicle did not have more than one vibration occurring.

Preliminary Visual/Physical Inspection

1. Inspect for aftermarket equipment and modifications which could affect the operation of the vehicle rotating component systems.
2. Inspect the easily accessible or visible components of the vehicle rotating component systems for obvious damage or conditions which could cause the symptom.
3. Inspect the tire inflation pressures for the proper pressure.

Diagnostic Aids

Improper component routing or isolation, or components which are worn or faulty may be the cause of intermittent conditions that are difficult to duplicate. If the vibration concern could not be duplicated by following the steps of the Vibration Diagnostic Process, refer to VIBRATION DIAGNOSTIC AIDS .

Classifying The Symptom

Axle Shaft symptoms can usually be classified into the following categories.

1. Leaks
2. Noises
3. Vibrations

For leak and noise related concerns, see

SYMPTOM LIST

. For additional information not addressed here, see TROUBLE SHOOTING in GENERAL INFORMATION. For vibration related symptoms, refer to

VIBRATION DIAGNOSIS & CORRECTION

under DIAGNOSTIC STARTING POINT.

Visual/Physical Inspection

1. Inspect the system for aftermarket devices which could affect the operation of the axle shafts.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «CLICK NOISE IN TURNS»(ref-166336-S26780251482004091700000) under TROUBLE SHOOTING.
2. «CLUNK WHEN ACCELERATING FROM COAST»(ref-166336-S19507730522004091700000) under TROUBLE SHOOTING.
3. «CLUNK NOISE WHEN ACCELERATING DURING TURNS»(ref-166336-S35818678662004091700000) under TROUBLE SHOOTING.
4. «SHUDDER ON ACCELERATION AT LOW SPEED»(ref-166336-S41972593412004092100000) under TROUBLE SHOOTING.

Noise Diagnosis

Any gear-driven unit produces a certain amount of noise that is normal and that conventional repairs or adjustment cannot eliminate. Slight noise that is heard only at a certain speed or under unusual or remote conditions is acceptable. For example, this noise tends to reach a peak at speeds from 40-60 MPH depending upon road and load conditions, or upon gear ratio and tire size. Noise of this kind does not indicate trouble in the axle assembly.

When an axle is suspected of being noisy, make a thorough test in order to determine whether the noise originates in the tires, road surface, wheel bearings, engine, transmission, driveshaft, or axle assembly.

Front differential assembly symptoms can usually be classified into the following categories

1. Leaks
2. Noises
3. Vibrations

For leak and noise related concerns, see

SYMPTOMS LIST

. For additional information not addressed here, see TROUBLE SHOOTING in GENERAL INFORMATION. For vibration related symptoms, refer to

VIBRATION DIAGNOSIS & CORRECTION

under DIAGNOSTIC STARTING POINT.

1. Inspect the system for loose or missing fasteners.
2. Inspect the system for loose or leaking components.
3. Inspect the system for obvious damage or conditions which may cause the symptom.

Symptoms List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. See «FRONT DIFFERENTIAL ASSEMBLY NOISES»(ref-166336-S12819976692004092300000) .
2. See «NOISY IN DRIVE»(ref-166336-S33753299552004092300000) under TROUBLE SHOOTING.
3. See «NOISY WHEN COASTING»(ref-166336-S01276191372004092300000) under TROUBLE SHOOTING.
4. See «INTERMITTENT NOISE»(ref-166336-S28573592052004092300000) under TROUBLE SHOOTING.
5. See «CONSTANT NOISE»(ref-166336-S07791497292004092300000) under TROUBLE SHOOTING.
6. See «NOISY ON TURNS»(ref-166336-S14950638462004092300000) under TROUBLE SHOOTING.
7. See «FRONT DIFFERENTIAL ASSEMBLY LUBRICANT LEAK DIAGNOSIS»(ref-166336-S01807764962004092300000) under TROUBLE SHOOTING.

Driveshaft symptoms can usually be classified into the following categories.

1. Leaks
2. Noises
3. Vibrations

For leak and noise related concerns, see

SYMPTOM LIST

. For additional information not addressed here, see TROUBLE SHOOTING under appropriate DRIVE AXLE article in BASIC TROUBLE SHOOTING in GENERAL INFORMATION. For vibration related symptoms, refer to

VIBRATION DIAGNOSIS & CORRECTION

under DIAGNOSTIC STARTING POINT.

1. Inspect for aftermarket devices, which could affect the operation of the vehicle. See «AFTERMARKET ADD-ON ACCESSORIES»(ref-166336-S40322980522004092000000) under VIBRATION DUPLICATED, COMPONENT NOT IDENTIFIED under VIBRATION DIAGNOSTIC AIDS.
2. Inspect the easily accessible or visible system components for obvious damage or conditions, which could cause the symptom.
3. Verify the exact operating conditions under which the concern exists. Note factors such as vehicle speed, road conditions, ambient temperature, and other specifics.
4. Compare driving characteristics or sounds, if applicable, to a known good vehicle and make sure you are not trying to correct a normal condition.

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. See «RATTLE NOISE»(ref-166336-S24389563492004092200000) under TROUBLE SHOOTING.
2. See «UNIVERSAL JOINT NOISE»(ref-166336-S00298173832004092200000) under TROUBLE SHOOTING.
3. See «PING, SNAP, OR CLICK NOISE»(ref-166336-S14761413552004092200000) under TROUBLE SHOOTING.
4. See «KNOCK OR CLUNK NOISE»(ref-166336-S26894309452004092200000) under TROUBLE SHOOTING.
5. See «SCRAPING NOISE»(ref-166336-S41975428372004092200000) under TROUBLE SHOOTING.
6. See «MOANING NOISE»(ref-166336-S22009561452004092200000) under TROUBLE SHOOTING.
7. See «WHIRRING OR SQUEALING NOISE»(ref-166336-S08714738702004092200000) under TROUBLE SHOOTING.
8. See «SQUEAK NOISE»(ref-166336-S27588431622004092200000) under TROUBLE SHOOTING.
9. See «SHUDDER ON ACCELERATION AT LOW SPEED»(ref-166336-S41972593412004092100000) under TROUBLE SHOOTING.

Strategy Based Diagnostics

Review the system operations in order to familiarize yourself with the system functions. See REAR DIFFERENTIAL ASSEMBLY and AXLE SHAFTS under DESCRIPTION & OPERATION. All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system problem. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer to Strategy Based Diagnosis in General Information.

1. Inspect for aftermarket devices, which could affect the operation of the vehicle.
2. Inspect the easily accessible or visible system components for obvious damage or conditions, which could cause the symptom.
3. Check for the correct lubricant level and the proper viscosity.
4. Verify the exact operating conditions under which the concern exists. Note factors such as vehicle speed, road conditions, ambient temperature, and other specifics.
5. Compare the driving characteristics or sounds, if applicable, to a known good vehicle and make sure you are not trying to correct a normal condition.

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom. For noise and leak related symptoms, see TROUBLE SHOOTING under appropriate DRIVE AXLE article in BASIC TROUBLE SHOOTING in GENERAL INFORMATION.

1. See «VIBRATION DIAGNOSIS & CORRECTION»(ref-166336-S00102030642004091700000) under DIAGNOSTIC STARTING POINT.
2. See appropriate AUTOMATIC TRANSMISSION article in TRANSAXLE/TRANSMISSIONS.
3. See MANUAL TRANSMISSION NOISY (if equipped) under TROUBLE SHOOTING in appropriate MANUAL TRANSMISSIONS article in TRANSAXLE/TRANSMISSIONS.
4. See «DRIVESHAFT»(ref-166336-S42389525372004092100000) under SYMPTOMS.
5. See CLUTCH NOISY under TROUBLE SHOOTING in appropriate CLUTCH article in TRANSAXLE/TRANSMISSIONS.
6. See «REAR DIFFERENTIAL ASSEMBLY NOISES»(ref-166336-S25071708722004092300000) under TROUBLE SHOOTING.
7. See «NOISY IN DRIVE»(ref-166336-S33753299552004092300000) under TROUBLE SHOOTING.
8. See «NOISY WHEN COASTING»(ref-166336-S01276191372004092300000) under TROUBLE SHOOTING.
9. See «INTERMITTENT NOISE»(ref-166336-S28573592052004092300000) under TROUBLE SHOOTING.
10. See «CONSTANT NOISE»(ref-166336-S07791497292004092300000) under TROUBLE SHOOTING.
11. See «NOISY ON TURNS»(ref-166336-S14950638462004092300000) under TROUBLE SHOOTING.
12. See «REAR DIFFERENTIAL ASSEMBLY LUBRICANT LEAK DIAGNOSIS»(ref-166336-S30080299902004092300000) under TROUBLE SHOOTING.

1. Inspect the system for the following: Loose or missing fasteners. Obvious damage or conditions which may cause the symptom.
2. Check the system for proper operation. See «LOCKING DIFFERENTIAL DIAGNOSIS»(ref-166336-S13802919972004092700000) and «LIMITED SLIP DIFFERENTIAL DIAGNOSIS»(ref-166336-S18312263892004092700000) under TROUBLE SHOOTING.

Refer to a system diagnostic procedure from the following list in order to diagnose the symptom

1. See «LOCKING REAR AXLE DOES NOT LOCK»(ref-166336-S00320796942004092700000) under TROUBLE SHOOTING.
2. See «LOCKING REAR AXLE LOCKS IN TURNS»(ref-166336-S30760240762004092700000) under TROUBLE SHOOTING.
3. See «LIMITED SLIP DIFFERENTIAL CHATTERS IN TURNS»(ref-166336-S42507038582004092700000) under TROUBLE SHOOTING.
4. See «LOCKING REAR DRIVE AXLE CHATTERS IN TURNS»(ref-166336-S03732827602004092700000) under TROUBLE SHOOTING.
5. See «NOISE IN ADDITION TO NORMAL CLUTCH ENGAGEMENT»(ref-166336-S27362208412004092700000) under TROUBLE SHOOTING.

VIBRATION DIAGNOSTIC AIDS

Note. If you have not reviewed the Diagnostic Starting Point - Vibration Diagnosis and completed the Vibration Analysis tables as indicated, refer to VIBRATION DIAGNOSIS & CORRECTION under DIAGNOSTIC STARTING POINT 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 4 main conditions. Refer to the appropriate condition from this list.

1. «VIBRATION INTERMITTENT OR NOT DUPLICATED»(ref-166336-S04526134562004092000000)
2. «VIBRATION DUPLICATED, COMPONENT NOT IDENTIFIED»(ref-166336-S33616611392004092000000)
3. «VIBRATION DUPLICATED, DIFFICULT TO ISOLATE/BALANCE COMPONENT»(ref-166336-S12886000652004092000000)
4. «VIBRATION DUPLICATED, APPEARS TO BE POTENTIAL OPERATING CHARACTERISTIC»(ref-166336-S40808675892004092000000)

VIBRATION ANALYSIS - ROAD TESTING

Note. For Vibration Analysis - Road Testing, refer to illustrations. (Scheme 1)- (Scheme 4).

Scheme 1

Scheme 2

Scheme 3

Scheme 4

FRONT DIFFERENTIAL ASSEMBLY LUBRICANT LEAK DIAGNOSIS

Front axle lubricant leaks can occur at the following locations

1. Axle shaft oil seals.
2. Differential carrier assembly mating surface.
3. Drain plug.
4. Fill plug.
5. Inner axle tube assembly to differential carrier assembly mating surface.
6. Pinion yoke oil seal.
7. Vent tube.

REAR DIFFERENTIAL ASSEMBLY LUBRICANT LEAK DIAGNOSIS

Rear axle lubricant leaks can occur at the following locations

1. Axle Tube To Differential Carrier Housing Joint
2. Axle Shaft Oil Seal
3. Axle Housing Porosity
4. Differential Housing Cover Gasket
5. Drain Plug
6. Fill Plug
7. Pinion Yoke Oil Seal
8. Vent Tube

LOCKING DIFFERENTIAL DIAGNOSIS

1. Place the vehicle on a frame-contact hoist, allowing free rotation of the rear wheels.
2. Hold one wheel stationary. Slowly rotate the other wheel approximately 1/2 revolution per second in both the forward and reversed directions. The wheel should rotate freely. The differential is locking and is broken if both wheels attempt to turn together.
3. Raise the hoist to maximum height with one person in the vehicle.
4. Start the engine. Ensure that the engine is operating at low idle speed (warm engine).
5. Apply the service brake. Place the automatic transmission in drive. Depress the clutch and place the transmission in first gear with a manual transmission.
6. Lock one rear wheel by pulling one parking brake cable from under the vehicle with the aid of an assistant.
7. Release the service brakes or disengage the clutch slowly enough to start the free wheel turning. The locked rear wheel remains stationary.
8. Increase the speed of the free wheel. The differential will lock, causing the rotating wheel to stop or both wheels to turn at the same speed. The engine, if equipped with manual transmission, may stall. In order to cause the differential to lock, you may need to accelerate the engine until approximately 10 MPH is indicated on the vehicle speedometer. If the indicated speed can be increased beyond 20 MPH without causing the differential to lock, the unit is not functioning properly. Rapid release of the brakes or clutch, or rapid acceleration of the engine, will invalidate the test.
9. Lock the opposite rear wheel and repeat the procedure.

LIMITED SLIP DIFFERENTIAL DIAGNOSIS

1. Did you review the general description and perform the necessary inspections? If so, go to next step. If not, see «LOCKING/LIMITED SLIP REAR DIFFERENTIAL»(ref-166336-S33058290642004092700000) under DIAGNOSTIC STARTING POINT.
2. Measure the rotational force of the axle using the following procedure: Block the front wheels. Raise and support the vehicle. Remove the tire and wheel. Using the Front/Rear Spindle Remover (J-28733-B), measure the rotational force of the axle. See «AXLE ROTATIONAL FORCE SPECIFICATION»(ref-166336-S01909929932004092700000) . Repeat the procedure for the other axle. Does the force measure outside the specified range? If so, go to next step. If not, system is okay.
3. Repair the rear axle. Did you complete the repair? If so, go to next step.
4. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

AXLE ROTATIONAL FORCE SPECIFICATION