Section 00-04: Noise, Vibration and Harshness
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

SPECIAL SERVICE TOOL(S) REQUIRED
Description Tool Number
Belt Tension Gauge T63L-8620-A

These diagnosis charts are designed to take the technician through a step-by-step diagnosis procedure to determine the cause of a condition. It may not always be necessary to follow the chart to its conclusion. Perform only the Steps necessary to correct the condition. Then check operation of the system to ensure the cause has been found.

It is sometimes necessary to remove various components of the vehicle to gain access to the component to be tested. Refer to applicable Section for removal and installation of components. After verifying the condition has been corrected, ensure all components removed have been installed.   

PINPOINT TEST A: HIGH SPEED SHAKE

 

A1 ROAD TEST 

Yes
GO to A2.

No
Vehicle OK.

 

A2 INSPECT TIRES

Yes
GO to A3.

No
CHECK suspension components for misalignment, abnormal wear, or damage that may have contributed to the tire wear. CORRECT suspension concerns, and REPLACE damaged tires. PERFORM Road Test.

 

A3 INSPECT FRONT WHEEL BEARINGS

  • Spin front tires by hand to check for front wheel bearing roughness. Check bearing end play.
  • Is end play OK?




Yes
GO to A4.

No
REPLACE wheel hubs as necessary. PERFORM Road Test.

 

A4 WHEEL/TIRE RUNOUT ON VEHICLE

  • Measure wheel/tire assembly runouts on vehicle using Rotunda Radial Run-Out Gauge 007-00014 or equivalent. Assembly runout should be less than 1.14 mm (0.045 inch) radial and lateral. Warm up tires prior to taking measurement to eliminate slight flat spotting.
  • Is measurement in specification?
Yes
GO to A9.

No
GO to A5.

 

A5 WHEEL/TIRE RUNOUT OFF VEHICLE

  • Measure wheel/tire assembly from any position that exceeds 1.14 mm (0.045 inch) radial or lateral. Before removing wheel/tire assembly, mark wheel stud and corresponding bolt hole so assembly can be installed in same position. Remove assembly and mount on wheel balancer. Measure runout as in Step A4. Assembly runout should be less than 1.14 mm (0.045 inch) radial and lateral.
  • Is measurement in specification?
Yes
CHECK disc brake rotor and wheel hub bolt circle runout. GO to A8.

No
GO to A6.

 

A6 MATCH MOUNTING

  • Mark the high runout location on the tire and also on the wheel . Break the assembly down and rotate the tire 180 degrees (half-way around) on the wheel . Inflate the tire and measure the runouts.
  • Is wheel/tire assembly balanced?
Yes
BALANCE assembly and INSTALL on vehicle. Refer to Section 04-04. PERFORM Road Test.

No
If high spot is not within 101.6mm (4 inches) of first high spot on the tire, GO to A7.

 

A7 WHEEL RUNOUT

  • Dismount tire and mount wheel on wheel balancer. Measure runouts on both flanges. Runout should be less than 1.14 mm (0.045 inch) radial and lateral.
  • Is there proper runout?




Yes
LOCATE and MARK low spot on wheel and INSTALL tire matching high spot on wheel. BALANCE assembly and PERFORM Road Test.

No
REPLACE wheel. CHECK runouts on new wheel. If new wheel is within limits, LOCATE and MARK the low spot. INSTALL tire, matching high spot of tire with low spot of wheel. BALANCE assembly and INSTALL on vehicle. PERFORM Road Test.

 

A8 AXLE, ROTOR AND BOLT CIRCLE RUNOUTS

  • For rear wheel positions, remove rotor and measure axle flange face runout (less than 0.254mm (0.010 inch)). Bolt circle runout (less than 0.397mm (0.015 inch)) and rotor pilot radial runout (less than 0.152mm (0.006 inch)).
  • For front wheel positions, measure rotor lateral runout (greater than 0.127mm (0.005 inch)).
  • For front wheel position, measure lateral runout (less than 0.05mm (0.002 inch)) bolt circle runout (less than 0.35mm (0.014 inch)).
  • Are measurements correct?




Yes
REPLACE wheel and GO to A9.

No
REPLACE rotor (front wheel positions) wheel hub (front wheel position) or axle shaft (rear wheel positions) and PERFORM Road Test.

 

A9 FRONT TIRES

  • Spin front tires with a wheel balance spinner while vehicle is raised on hoist. Feel for vibration in fender or while seated in vehicle.
  • Is vibration felt?
Yes
BALANCE front wheel(s). PERFORM Road Test.

No
GO to A10.

 

A10 REAR TIRES

  • Engage drivetrain while vehicle is raised on hoist. Carefully accelerate the drive wheels while feeling for vibration.
  • Is vibration felt?
Yes
GO to A11.

No
GO to A13.

 

A11 DRIVETRAIN

  • Remove rear wheels, secure brake drums, if so equipped by installing wheel hub bolt nuts , reversed. Carefully accelerate the drivetrain while feeling for vibration.
  • Is vibration felt?
Yes
GO to A12.

No
BALANCE rear wheels. PERFORM Road Test.

 

A12 REAR DISC BRAKE ROTORS

  • Remove the brake drums or rotors. Carefully accelerate the drivetrain while feeling for vibration.
  • Is vibration felt?
Yes
GO to Pinpoint Test D.

No
REPLACE brake drums . PERFORM Road Test.

 

A13 WHEEL BALANCE

  • Balance all wheels not previously balanced. Road test vehicle.
  • Are wheels balanced?
Yes
Vehicle OK.

No
GO to A14.

 

A14 SUBSTITUTE WHEELS AND TIRES

  • Substitute a known good set of wheels and tires. Road test vehicle.
  • Is vibration felt?
Yes
GO to Pinpoint Test D.

No
INSTALL the original tire/wheel assemblies, one by one, road testing at each step, until the defective tire(s) is identified. REPLACE tire(s) as necessary and RETEST.

  

PINPOINT TEST B: TIP-IN MOAN

 

B1 AIR CLEANER 

  • Check air cleaner for proper installation of base gasket, air cleaner element and air inlet duct assembly.
  • Are components properly installed?
Yes
GO to B2.

No
CORRECT condition and PERFORM Road Test. If moan persists, GO to B2.

 

B2 POWERTRAIN RESONANCE

  • Loosen all torque converter housing-to-engine retaining bolts 3/4 turn and road test. Tighten bolts after test.
  • Is moan reduced or eliminated?
Yes
REPLACE or INSTALL crank damper as indicated; refer to Section 03-01A (3.8L) or Section 03-01B (5.0L HO and 5.0L Cobra). If the moan still persists, GO to
B3.

No
GO to B3.

 

B3 ENGINE MOUNTS

  • Normalize engine mounts by loosening them and, with engine running, shifting transmission from NEUTRAL to DRIVE and back to NEUTRAL. With manual transmission, load engine by slipping clutch in gear. Tighten mounting bolts and road test.
  • Is moan reduced or eliminated?




Yes
Vehicle OK.

No
GO to B4.

 

B4 EXHAUST SYSTEM

  • Warm up system to normal operating temperature. Loosen all hanger attachments and reposition hangers until they hang free and straight. Then loosen all flange joints and, with engine running, shift transmission from NEUTRAL to DRIVE and back to NEUTRAL (or load engine with clutch). Tighten all hanger clamps and flanges. Road test vehicle.
  • Is moan reduced or eliminated?




Yes
Vehicle OK.

No
GO to Pinpoint Test C.

  

PINPOINT TEST C: ENGINE ACCESSORY VIBRATION

 

C1 ENGINE RUN-UP 

  • Run-up to problem rpm observed in road test, with vehicle stationary.
  • Does vibration occur?
Yes
GO to C2.

No
PERFORM stall test in DRIVE with brakes locked (or load engine by slipping clutch in gear with manual transmission). If vibration occurs, GO to Pinpoint Test B.

 

C2 DRIVE BELTS AND PULLEYS

  • With engine stopped, inspect all engine accessory drive belts and pulleys for wear or damage, and check belt tension, using Belt Tension Gauge T63L-8620-A or equivalent.
  • Automatic tensioners have belt wear indicator marks. If the indicator mark is not between the min and max marks, the belt is worn or an incorrect belt is installed.
  • Are belts or pulleys worn or damaged?




Yes
REPLACE worn or damaged belts or pulleys. CORRECT belt tension. GO to C3.

No
GO to C3.

 

C3 MOUNTING HARDWARE

  • Inspect mounting brackets and adjusting components for proper alignment and tightness.
  • Are mounting and adjusting components secure?
Yes
GO to C4.

No
ALIGN and TIGHTEN mounting hardware to specifications. CORRECT belt tension. START UP engine and run-up to problem rpm. If vibration still exists, GO to C4.

 

C4 ENGINE IDLING

  • With engine idling, visually check all accessory drive belts and pulleys for misalignment, runout or irregular motion. Maximum runout is 3mm (1/8 inch).
  • Increase engine rpm.
  • Is runout within specifications?
Yes
GO to C5.

No
REPLACE pulley.

 

C5 DRIVEBELT ALIGNMENT

  • With engine idling, visually check all accessory drive belts and pulleys for misalignment, runout or irregular motion. Maximum runout is 3mm (1/8 inch).
  • Increase engine rpm.
  • Does belt ride up on pulley?
Yes
REPLACE that pulley.

No
REPLACE belt. GO to C6.

 

C6 ACCESSORY DRIVE BELT NOISE

  • Check for "chirps" or squeal in a poly-vee belt by spraying a small amount of water on the grooved side of the belt (use a spray bottle or equivalent).
  • Does the noise change?
Yes
CHECK for misalignment. CHECK tensioner position. CHECK for worn belt. SERVICE/REPLACE as required.

No
CHECK accessory bearings. Refer to Section 03-00. REPLACE as required. GO to C7.

 

C7 ACCESSORIES

  • Run-up engine to problem rpm and, with stethoscope-type device, check each component.
  • If the source cannot be detected by probing, remove each belt, one at a time, until vibration goes away.
  • Is noisy component located?
Yes
REPLACE drive belt . If vibration still exists, SERVICE or REPLACE component.

No
Possible engine component imbalance. This situation is possible, but unlikely.

  

PINPOINT TEST D: DRIVESHAFT VIBRATION

 

D1 WHEELS AND TIRES 

  • Verify that the observed condition is not a high speed shake caused by wheels/tires.
  • Is condition a high speed shake?
Yes
PERFORM Pinpoint Test A (High Speed Shake Diagnosis) for drive-wheel runout and balance procedures.

No
GO to D2.

 

D2 DRIVESHAFT

  • Inspect driveshaft for undercoating or physical damage. Check index marks (yellow paint daubs) on rear of driveshaft and rear axle universal joint flange . These marks should be no more than 90 degrees apart.
  • Are marks more than 90 degrees apart?
Yes
CLEAN off undercoating or REPLACE damaged driveshaft. If index marks are misaligned, GO to D6. CHECK for vibration at road test speed. If still present, GO to
D3.

No
GO to D3.

 

D3 DRIVESHAFT RUNOUT

  • With vehicle on hoist, measure runout at front, center and rear of driveshaft . Maximum runout is 0.89 mm (0.035 inch).
  • Is runout within specifications?
Yes
GO to D4.

No
MARK the rear runout high point. GO to D5.

 

D4 DRIVESHAFT RE-INDEXING AT TRANSMISSION

  • Note or mark indexing of driveshaft to transmission and rear axle universal joint flange . Disconnect the driveshaft, re-index 180 degrees at transmission only and reconnect. Check runout at front and center of driveshaft. Maximum runout is 0.89 mm (0.035 inch).

    NOTE: While driveshaft is removed from vehicle and manipulate U-joints in each direction of rotation. If a U-joint feels stiff or has a "lumpy," "gritty" feel in any direction, replace U-joints or driveshaft .

  • Is it within specification?
Yes
CHECK for vibration at road test speed. If still present, mark rear runout high point. GO to D5.

No
GO to D6.

 

D5 DRIVESHAFT RE-INDEXING AT AXLE

  • Note or mark indexing of rear axle universal joint flange . Disconnect the driveshaft . Re-index 180 degrees at rear axle housing and connect. Check runout at rear of driveshaft . Maximum runout is 0.89 mm (0.035 inch).
  • Is it within specification?




Yes
CHECK for vibration at road-test speed. If still present, GO to D7.

No
GO to D6.

 

D6 REAR AXLE UNIVERSAL JOINT FLANGE

  • Compare the two high points of runout marked in Test Steps C3 and C4.
  • Are marks within 25mm (1 inch) of each other?
Yes
REPLACE driveshaft . RECHECK vibration.

No
REPLACE rear axle universal joint flange . CHECK driveshaft runout and road test for vibration. If still present, GO to D7.

 

D7 DRIVESHAFT VIBRATION

  • The driveshaft can be re-indexed at both the rear axle and transmission to minimize system imbalance. Refer to driveshaft indexing procedure.
  • Is driveshaft balanced?
Yes
Vehicle OK.

No
REFER to driveshaft balancing Test Step D8 , if vibration still present.

 

D8 AXLE PINION NOISE DAMPER

  • If vibration still exists after balancing driveshaft , install an axle pinion damper, as outlined.
  • Is vibration still present?
Yes
Vehicle OK. REPLACE driveshaft if vibration still persists. GO to D9.

No
REFER to Section 05-00.

 

D9 DRIVESHAFT BALANCING — CLAMP METHOD

  • Mark rear of driveshaft in four equal parts and number them 1, 2, 3 and 4.
  • Install hose clamp with screw at position No. 1.
  • Operate driveline at speed at which customer complained of vibration.
  • Rotate clamp to each of the other three positions and check for vibration.
  • Is vibration the same?




Yes
GO to D12.

No
ROTATE clamp screw to a mid-point between the two positions. GO to D10.

 

D10 INSTALL SECOND CLAMP

  • Install another clamp, with screw in same position as first clamp.
  • Operate vehicle at speed at which customer complained of vibration.
  • Is vibration minimal?




Yes
Condition corrected.

No
GO to D11.

 

D11 REPOSITION CLAMP

  • Rotate screws of clamps equally away from each other about 12.7mm (1/2 inch).
  • Operate vehicle at speed at which customer complained of vibration.
  • Is vibration minimal?




    NOTE: If vibration is corrected with the addition of clamps, the clamps will be left on the driveshaft permanently. Check clamp clearance after installation to prevent any contact with floorpan or other parts.

Yes
Condition corrected.

No
GO to D12.

 

D12 ROAD TEST

  • Install wheels and tires.
  • Road test vehicle.
  • Is vibration minimal?

    NOTE: Vibration felt on hoist may be acceptable during road test.

Yes
Condition corrected.

No
GO to Pinpoint Test A.

 

PINPOINT TEST E: TIRE/WHEEL RUNOUT

 

E1 TIRE WHEEL BEARING INSPECTION

  • Raise vehicle, inspect tires and check wheel bearings .
  • Are bearings OK?
Yes
GO to E2.

No
SERVICE bearings. GO to E2.

 

E2 BALANCE TIRES

  • Balance tires and place back on vehicle.
  • Does vehicle function properly?
Yes
Vehicle OK.

No
GO to E3.

 

E3 ROTATE TIRES

  • Rotate tire and wheel assembly. Front to rear, and rear to front.
  • Does vehicle function properly?
Yes
Vehicle OK.

No
GO to E4.

 

E4 CHECK RUNOUT

  • Check total radial runout and total lateral runout of tire/wheel assembly.

    NOTE: All runout values shown are for front wheels. Runout values should be increased 0.127mm (0.005 inch) for rear wheels. If both radial and lateral runouts are excessive, resolve lateral concerns before proceeding with radial service procedures.

  • Is runout within specifications?
Yes
GO to E5.

No
GO to E6.

 

E5 INDEX TIRE ON WHEEL

  • Index tire on wheel . Align highest runout point to wheel low runout point.
  • Is total radial runout less than 1.01mm (0.040 inch)?
Yes
GO to E6.

No
GO to E7.

 

E6 BALANCE TIRES

  • Check and balance tires.
  • Road test.
  • Is vibration eliminated?
Yes
Service complete.

No
In some cases a vibration concern may be caused by tire internal construction inducing force variations which cannot be detected through runout measurement. This condition is diagnosed by installing tire/wheel assemblies (one at a time) from a good vehicle to isolate the offending tire(s). REPLACE tires as necessary. BALANCE tires. PERFORM Road Test.

 

E7 CHECK WHEEL RADIAL RUNOUT

  • Check wheel radial runout and ensure it is correct.

    NOTE: Although maximum wheel runout shown exceeds acceptable total tire/wheel assembly runout, acceptable assembly runout may be achieved by indexing tire on wheel.

  • Is wheel runout less than 1.14mm (0.045 inch)?
Yes
REPLACE tire. BALANCE tire. PERFORM Road Test. If still not OK, CHECK radial runout.

No
REPLACE wheel. BALANCE tire. PERFORM Road Test. If still not OK, CHECK radial runout.