TCC rpm oscillation

Tach bounces up and down a few hundered rpm while cruising in lockup:


Another common problem / concern of this transmission and more pronounced with added engine power or higher mileage.  This generally happens when the valve body has excess wear in the TCC regulated apply valve area but also has other causes.  Excessive fluid leakage in this area of the valve body causes TCC apply pressure loss and can lead to uncontrollable TCC operation which causes the engine rpm to bounce up and down a bit.  This problem is noticed most after driving a while and speeds between 42 and 70mph and in 4th gear.  There are other causes to this problem that can be from a hard and shrunken TCC regulated apply valve end plug o-ring, worn or shrunken teflon seals on the input shaft, a bad o-ring on the input shaft that seals in the torque converter, a faulty torque converter clutch, and even a bad pressure control solenoid.  Another common occurance is a worn out sleeve in the channel plate that supports the input shaft.  A dirty MAF sensor can also have effect on this condition and should also be inspected.  In the service field it has been found on occasion that a complete PCM/TCM reflash can also address this problem, though I have found that even if this helps the problem can come back in a short matter of time.  Code P0741 may be found in the pcm memory as a stored code and is described as Torque Converter Clutch Stuck Off.  When this happens adaptives shifts are disabled, TCC operation is disabled, and 4th gear can be disabled.  Generally a new or reman / repaired valve body will correct this condition and a new EPC solenoid is always suggested as well.  The TCC/PWM solenoid is rarely ever at fault for this condition but is also a good idea to replace if you are reparing the transmission.  Again the valve body is the common cure BUT not always the culprit and certainly not the whole problem after this has been happening for a while.  Any time a torque converter fails there will be debris going back into the trans.  There is a pressure relief valve in the channel plate that will collect debris from a bad torque converter and reduce cooler flow, cause trans to run hot, and greatly effect TCC operation and can destroy a new converter in a matter of miles if this isnt carefully inspected or upgraded.  The best way to verify proper operation as commanded by the pcm is with a scan tool by viewing TCC slippage rpm, TCC duty cycle, EPC data, and checking any codes and making sure the engine is running properly and a misfire is not a false sense of a torque converter problem or shudder.
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