Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 597 (AUTOMATIC TRANSAXLE, 4T65-E DIAGNOSTICS (TROUBLESHOOTING))TROUBLESHOOTINGTORQUE CONVERTER REPLACEMENT GUIDE

1999 GMC Forward Control 5.7 R, Automatic

Torque Converter Replacement Guide

1999 GMC Forward Control 5.7 R, AutomaticSECTION Torque Converter Replacement Guide

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

Condition	Action
Fluid
Transmission Fluid Oxidized/Discolored No metal debris Clutch fiber material	Do not replace the torque converter. Refer to Transmission Fluid Checking Procedure .
Transmission Fluid Contaminated with Engine Coolant/Oil	Replace the torque converter. Refer to Torque Converter Cover Replacement (LA1) or Torque Converter Cover Replacement (LY7) .
Transmission Fluid Contaminated with Sludge/Metal Particles	Replace the torque converter if the following conditions are found: Pump damage Drive sprocket support damage Turbine/stator shaft damage No damage found in transmission Do not replace the torque converter for other transmission component damage.
Fluid Leaks from Torque Converter	Perform the powder/dye leak check Refer to Fluid Leak Diagnosis . Replace the torque converter if the following conditions are found: Leak present at weld areas-hub, lug, or closure weld Hub surface is damaged-scored, raised/transferred metal Bushing is damaged
Function/Appearance
Torque Converter Discolored/Overheated	Replace the torque converter. Refer to Torque Converter Cover Replacement (LA1) or Torque Converter Cover Replacement (LY7) .
Broken/Cracked Flexplate	Replace the torque converter. Refer to Torque Converter Cover Replacement (LA1) or Torque Converter Cover Replacement (LY7) .
Stripped Converter Bolt Holes	Replace the torque converter. Refer to Torque Converter Cover Replacement (LA1) or Torque Converter Cover Replacement (LY7) .
Torque Converter Pilot Damaged	Replace the torque converter. Refer to Torque Converter Cover Replacement (LA1) or Torque Converter Cover Replacement (LY7) .
Torque Converter Ballooning	Replace the torque converter if end play exceeds 0.7mm (0.3 in) using J 35138 .
Driveability - Non TCC
Harsh Gear Shifts-Non TCC	Do not replace the torque converter. Refer to Symptoms - Automatic Transmission .
No Drive/Slips in Drive-Non TCC	Do not replace the torque converter until completing all engine and transmission diagnostics. Refer to Slips in Drive or No Drive .
Idle Surge/Rough Idle	Do not replace the torque converter. Refer to Rough, Unstable, or Incorrect Idle and Stalling in Engine Controls-3.4L.
Poor Acceleration above 48 km/h (30 mph) - Launch	Do not replace the torque converter until completing all engine and transmission diagnostics. Refer to Lack of Power, Sluggishness, or Sponginess in Engine Controls-3.4L. Refer to Hesitation, Sag, Stumble in Engine Controls-3.4L. Refer to Symptoms - Automatic Transmission .
DTC P0741-TCC Stuck OFF/High Slip-Intermittent Only	Do not replace the torque converter. Refer to DTC P0741 (3.4L) or DTC P0741 (3.6L) .
DTC P0741-TCC Stuck OFF/High Slip	Refer to DTC P0741 (3.4L) or DTC P0741 (3.6L) .
DTC P0742-TCC Stuck ON	Do not replace the torque converter. Refer to DTC P0742 (3.4L) or DTC P0742 (3.6L) .
DTC P1887-TCC Release Switch	Do not replace the torque converter. Refer to DTC P1887 (3.4L) or DTC P1887 (3.6L) .
TCC Apply/Release Shudder	Refer to Converter Clutch Apply Rough, Slips, or Shudders .
TCC Chuggle	Refer to Symptoms - Engine Mechanical in Engine Mechanical-3.4L. Refer to Surges/Chuggles in Engine Mechanical-3.4L. Refer to Symptoms - Automatic Transmission .
Noise and Vibration
Noise-Whine	Refer to Symptoms - Automatic Transmission . Do not replace the torque converter if noise is present in Neutral/Park. Refer to Symptoms - Engine Mechanical in Engine Mechanical-3.4L.
Vibration-Out of Balance	Refer to Flexplate/Torque Converter Vibration Test . Refer to Vibration Analysis - Engine in Vibration Diagnosis and Correction.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.