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All Info About Auto Repair: Diagnose Automatic Transmission Problems Part 4
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Diagnose Automatic Transmission Problems Part 4

What you can do to diagnose an automatic transmission problem.
» Engine/Transmission Relations
» Transmission or Transaxle?
» Transmission Testing
» Transmission Leak Tests
» Diagnosis By Symptom

Transmission Fluid Leak Tests

This one is kind of self-explanatory. You can use a special dye to find a transmission leak. Oil-soluble aniline or fluorescent dyes premixed at the rate of one half teaspoon of dye powder to one half pint of transmission fluid may be useful in locating the source of a leakage. If the transmission fluid in the radiator cooler leaks into the coolant system, a black light must be used to see the fluorescent dye solution. Fortunately there are not too many places an automatic transmission can leak. To do a through check:

  1. Check speedometer cable connector at the transmission. Replace rubber 0-ring, if necessary.

  2. Check oil pan gasket. Tighten attaching bolts to proper torque and/or replace gasket, if necessary.

  3. Check fluid filler tube connection at transmission case. Check filler tube 0-ring seal for damage. If leakage is found, install new short oil inlet tube and 0-ring seal or clean the area and apply sealer around the tube.

  4. Check fluid lines and fitting between transmission and cooler in radiator tank for looseness, wear, or damage. If leakage is found, tighten fitting to proper torque, or replace the damaged parts.

  5. Check engine coolant in radiator. If transmission fluid is present in coolant, the cooler in the radiator is leaking.

  6. If leakage is found at the downshift control lever and manual lever shaft, replace seal.

  7. Inspect pipe plug on left rear side of transmission case. Tighten plug or replace, if necessary.

  8. Fluid leakage from the converter housing may be caused by engine oil leakage past the rear main bearing, by oil galley plug leaks, or by power steering fluid leakage from steering system. Determine the exact cause of the leak before beginning service procedures.

If you have leakage from the converter housing, here's what you can do to isolate the cause:

  1. Fluid leaking by the front pump seal lip will tend to move along the impeller hub and onto the back of the impeller housing.

  2. Fluid leakage by the outside diameter of the seal and front pump body will follow the same path as the leaks from the front pump seal.

  3. Fluid that leaks from a front pump-to-case bolt will be deposited on the inside of the converter housing only. Fluid will not be deposited on the back of the converter.

  4. Leakage by the front pump-to-case gasket may cause fluid to seep down between the front of the case and converter housing.

  5. Fluid leakage from the converter-to-flywheel stud weld will appear at the outside diameter of the converter on the back face of the flywheel, and in the converter housing only near the flywheel.

  6. The following areas of possible leakage should be checked to determine if engine oil is leaking.

    1. Leakage at the rocker arm cover may allow oil to flow over the converter housing and cylinder block, causing oil to be present in or at the bottom of the converter housing and cylinder block, causing oil to appear at the bottom of the converter housing.

    2. Oil galley plug leaks will allow oil to flow down the rear face of the block to the bottom of the converter housing.

    3. Leakage by the crankshaft seal will work back to the flywheel, then into the converter housing.

  7. Fluid leakage from other areas, such as the power steering system forward of the transmission, may cause fluid to appear around the converter housing due to blow-back or road draft. The following procedures should be used to determine the cause of leakage before any repairs are made.

    1. Check transmission dipstick for color of fluid. Original factory-fill fluid is dyed red. Unless the fluid has been changed, the color should assist in pinpointing the leak. Leakage due to road draft should be eliminated before checking the transmission for fluid leaks.

    2. Remove converter housing cover and clean off any fluid from the top and bottom of the converter housing, front of transmission case, and rear face of engine and oil pan.

    3. Start and run engine until transmission reaches normal operating temperature. Observe the back of the block and top of the converter housing for evidence of fluid leakage. Raise vehicle on a hoist and run engine at fast idle, then at engine idle, occasionally shifting to the drive and reverse ranges to increase pressure within the transmission. Observe the inside of the converter housing and front of the transmission case. Run the engine until fluid leakage is evident and the probable source of leakage can be determined.

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Additional Information provided courtesy of
ALLDATAdiy.com and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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