740/1740 codes tell you there is excessive slip at the TCC clutch. The engine and transmission output RPMs are constantly being monitored. You can compare the difference in the two RPM rates to determine transmission slip. If the RPM parameters for a slip in a given gear are met and TCC apply has not been commanded, you will see a gear ratio code. But, if the RPM parameters for a slip in a given gear are met and TCC apply has been commanded, you will see a (TCC slip) 740 code.
Sometimes the reason for the 740 code is not found within the transmission or torque converter. A restricted cooler or line is a good example. Using a fluid without the correct frictional qualities (the wrong fluid) may cause a 740 code. The hydraulic integrity of the valve body (worn bores) and the pump (excessive clearance or cross leaks) are two possible culprits that must also be eliminated. If all of these possibilities check out OK, it’s time to take a closer look at the torque converter.
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Article No.: TCTIP-09-05
Author: Ed Lee
Total Pages: 3
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