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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 66 (AUTOMATIC TRANSMISSION SERVICING)LUBRICATIONCHECKING FLUID LEVEL & CONDITION (4L80-E)CHECKING FLUID CONDITION
1999 GMC Forward Control 5.7 R, Automatic

Checking Fluid Condition

1999 GMC Forward Control 5.7 R, AutomaticSECTION Checking Fluid Condition
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check the fluid color. Is the fluid color Red? If so, go to next step. If not, go to step  11 .
  2. Is the fluid level satisfactory? If so, system is okay. If not, go to next step.
  3. Check the fluid. Is the fluid foamy? If so, go to step  8 . If not, go to next step.
  4. Check the fluid level. The proper fluid level should be in the middle of the cross-hatched area. Is the level high? If so, go to step  9 . If not, go to next step.
  5. The fluid will be low. Add fluid to the proper fluid level. After repairs, go to next step.
  6. Check for external leaks. Were any leaks found? If so, go to next step. If not, go to step  20 .
  7. Correct the leak condition. After repairs, go to step  20 .
  8. Is the fluid level too high? If so, go to next step. If not, go to step  10 .
  9. Remove excess fluid to the proper fluid level. Is the fluid level satisfactory? If so, go to step  20 .
  10. Check for contaminants in the fluid. Drain the fluid to determine the source of the contamination. Was the fluid drained? If so, go to step  15 .
  11. Is the fluid color non-transparent Pink? If so, go to next step. If not, go to step  14 .
  12. Replace the cooler. After repairs, go to step  15 .
    13. NOTE: Transmission fluid may turn dark with normal use. This does not always indicate oxidation or contamination.
  13. The fluid color should be Light Brown. Is the fluid color Light Brown? If so, go to next step.
    14. NOTE: A very small amount of material in the bottom pan is a normal condition, but large pieces of metal or other material in the bottom pan require a transmission overhaul.
  14. Drain the fluid to determine if the fluid is contaminated. Was the fluid contaminated? If so, go to next step. If not, go to step  18 .
  15. Overhaul the transmission. See appropriate OVERHAUL article in AUTOMATIC TRANSMISSIONS. Is the overhaul complete? If so, go to next step.
  16. Using scan tool, press clear TRANS ADAPT function. Are the reset procedures complete? If so, go to next step.
  17. Add new fluid. Is the procedure complete? If so, go to step  20 .
  18. Change the fluid and the filter. After repairs, go to step  19 .
  19. Are the reset procedures complete? If so, go to next step.
  20. Is the fluid level satisfactory? If so, system okay. If not, go to step  1 .
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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.