NOISE DIAGNOSIS SHOP MANUAL SUPPLEMENT

1987 CUTLASS CIERA AND FIRENZA MODELS/YEARS MODELS WITH THM 125C (MD9) TRANSAXLES The noise diagnosis covered in this bulletin is a supplement for the 1987 Oldsmobile Firenza, Calais, Cutlass Ciera, Delta 88, Ninety-Eight Chassis Service Manual, 125C Hydraulic Diagnosis Section.

- Before diagnosing the transaxle for a noise related condition, verify presence of noise in relation to drive range, vehicle speed, and engine rpm. Make certain the noise condition is not external to the transaxle. Refer to the noise and vibration analysis procedure, Section 7A of the service manual.

- Check for loose or misaligned components within the engine compartment which could contact the engine or transaxle during engine roll (engine torque movement).

- Follow the preliminary check procedure as outlined in the oil pressure chart included in the THM 125C Hydraulic Diagnosis Section. Carefully note:

- Transaxle fluid level - Condition of fluid (including presence of bubbles or contaminants on fluid level indicator) - Oil pressures as listed

THM 125C NOISE DIAGNOSIS

NOTE: FOR ALL FIGURE REFERENCES, REFER TO THE THM 125C UNIT REPAIR SECTION OF THE 1987 SERVICE MANUAL

CONDITION/ Circuit or System (General Description) Inspect For Cause

RATCHETING

Park System Parking Pawl Spring (707) Refer to Figure 46. -Broken, Mispositioned,

or Missing. NOISE IN ALL RANGES

Torque Converter Circuit Torque Converter - Torque Converter Internally Damaged.

(A whine which With Foot on Brake may be RPM or stops and Gear Selector load sensitive and/or in Drive, Depress when the Torque Accelerator to Converter Approximately 1200 RPM Clutch engages.) for No More than 6 Seconds (Stall Test). A Torque Converter Noise Increases Under Load.

Oil Pump System Oil Pump Assembly - Oil Pump Rotor/ Slide Thickness Refer to Figure 91 (A high pitch whine An Increase in Line Pressure which gets louder as will Vary an Oil Pump Noise. engine RPM increases (Note During Preliminary Check or is pressure Procedure) sensitive.) Pump Shaft Roller Bearing and Seal Assembly (354). Refer - Bearing Race or to Figure 89L. Roller Surfaces Rough or Pitted.

For Pump Cavitation

(A "popping" noise Fluid Level Indicator similar to popcorn for Bubbles. popping.) Transmission Oil Strainer (33). Refer to Figure 5. - Blocked Screen

- Filter Seam Leak

Transmission Oil Strainer Seal (32)Refer to Figure 5. - Mispositioned or Cut

For Pressure Buzz

(A buzz or high Verified by a Needle frequency rattle Vibration on a Pressure sound.) Gage. (Road test May Be Necessary.)

Pressure Regulator Valve (365) Refer to Figure 89L. - Calibration (Valve Shuttling)

Drive Link System

(A whine or growl With Engine Running and increases and fades Foot on Brake, Move the with vehicle speed, Gear Selector to Drive. most noticeable under The Noise Will Stop as the light throttle Transaxle Engages Drive Range. acceleration.) Drive Link Assembly (101) (A slipping chain Refer to Figure 78. - Stretched will cause a loud rattle during heavy acceleration.) Drive Sprocket (103) Refer to Figure 78. - Teeth Broken or Sheared - Bearing Surfaces Nicked or Scored

Drive Sprocket Support (109) Refer to Figure 45. - Bearing Outer Race Support Rough or Drive Sprocket Support Nicked. Bearing Assembly (108). - Bearing Race or Refer to Figure 41. Roller Surfaces Rough or Pitted.

Driven Sprocket (122) Refer to Figure 78. - Teeth Broken or Sheared - Bearing Surfaces Driven Sprocket Support Nicked or Scored (602) Refer to Figure 76. - Bearing Outer Race Support Rough or Driven Sprocket Support Nicked Bearing Assembly (601) Refer to Figure 76. - Bearing Race or RollerSurfaces Rough or Pitted NOISE DURING ACCELERATION

Drive Link System

Refer to:

Noise in All Ranges Drive Link Assembly

Torque Converter Circuit

Refer to:

Noise in All Ranges Torque Converter

For Pressure Buzz

Control Valve Assembly Circuit Valve Body Spacer Plate (20)(2.BL Models Only) (Buzz will cause a Refer to Figure 96. - Calibration (Spacer pulsation in the Plate) accelerator pedal.)

External Cooler Pipes Transaxle Cooler Pipes - Vibrating Together or Against other Vehicle Components.

SQUEAL AT LOW SPEED

Speedometer Assembly

(Most noticeable when Speedometer Driven Gear - Lack of Lubrication transmission is hot.) Shaft Seal

NOISE IN FIRST OR REVERSE

Input Gear Set

(A whine which is most Input Internal Gear (637) noticeable in first or Refer to Figure 65. - Gears Worn, Pitted reverse and is related to vehicle speed. The - Thrust Washer Mating whine may diminish or Surfaces Rough or go away after an Pitted upshift.)

Input Carrier Assembly - Gears Worn, Pitted, (640) Refer to Figure 65. Pinions Tilting

- Thrust Washer Mating Surfaces Rough or Pitted Input Sun Gear (642) Refer to Figure 65. - Gears Worn, Pitted

- Thrust Washer Mating Surfaces Rough or Pitted Reaction Gear Set

Refer to:

Noise in Second Reaction Gear Set

Final Drive Gear Set

Refer to:

Noise in Third and/or Final Drive Gear Set During Turns

NOISE IN SECOND

Input Gear Set

Refer to:

Noise in First or Input Gear Set Reverse

Reaction Gear Set

(A whine which is most Reaction Sun Gear (646) noticeable in second Refer to Figure 56. - Gears Worn, Pitted gear and is related to vehicle speed. The whine - Thrust Washer or may diminish or go away Thrust Bearing Mating after an upshift.) Surface Rough or Pitted

Reaction Carrier Assembly (665) Refer to Figure 56. - Gears Worn, Pitted, Pinions Tilting - Thrust Washer Mating Surfaces Rough or Pitted Reaction Sun Gear to Reaction Internal Gear Thrust Bearing (667). Refer to Figure 56. - Bearing Race or Roller Surfaces Rough or Reaction Internal Gear Pitted (668)Refer to Figure 56. - Gears Worn,Pitted

Lo and Reverse Clutch

(A light metallic Lo and Reverse Clutch Pack - Steel Plates Not Flat rattle noise most noticeable in second or third between 25 MPH - Clutch Pack Clearance and 40 MPH under coast or drive operation.) Case - Excess Plate to Case Clearance Due to Case Bore Machining.

Final Drive Gear Set

Refer to:

Noise in Third and/or During Turns Final Drive Gear Set

NOISE IN THIRD AND/OR DURING TURNS

Final Drive Gear Set

(A hum that may be Final Drive Internal noticeable in first, Gear (673) Refer to - Gears Worn, Pitted second and third, under Figure 49. light throttle - Thrust Washer or acceleration, and/or Thrust Bearing Mating during turns.) Surface Rough or Final Drive Sun Gear Pitted to Final Drive Internal Gear Thrust Bearing (674) Refer to Figure 49. - Bearing Race or Roller Surfaces Rough or Final Drive Sun Gear (675) Pitted Refer to Figure 49. - Gears Worn, Pitted

- Thrust Washer or Thrust Bearing Mating Surface Rough or Pitted Final Drive Sun Gear to Differential Carrier Thrust Bearing (676) Refer to Figure 49. - Bearing Race or Roller Surfaces Rough or Differential Carrier (678) Pitted Refer to Figure 49. - Gears Worn, Pitted, Pinions Tilting - Thrust Washer or Thrust Bearing Mating Surfaces Rough or Pitted

Differential Carrier to Case Thrust Bearing (681). Refer to Figure 49. - Bearing Race or Roller Surfaces Differential Pinions (685) Rough or Pitted Refer to Figure 49. - Gears Worn, Pitted

- Thrust Washer Mating Surfaces Rough Differential Side Gears or Pitted (687) Refer to Figure 49. - Gears Worn, Pitted

- Thrust Washer or Thrust Bearing Mating Surfaces Rough or Pitted

Lo and Reverse Clutch

Refer to:

Noise in Second Lo and Reverse Clutch

Wheel Bearing System

(Scratching or Hub and Bearing Assembly. scraping noise which Refer to Service Manual - Ruptured Seal or may increase or become Section 3C. Dented Race noticeable when turning.)

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.