1992 960 sedan. 205,000 miles. Beautifully running car. 1 problem, every time it shifts into 3rd and 4th it goes immediately into lock-up, which it can't handle at that moment and then will go back into the regular (slip mode?). It will go in and out of this sequence until I get to a speed that it can maintain lock-up and stay there. (hwy speed). I have separated the three electrical connections on the left side of the trans and cleaned and dialectic greased-did not help, have changed fluid and filter no result. Could this be a bad lock up solenoid? Where is that located? Is there a relay that could go bad that may be easier to repair?