I have a problem with the lock-up clutch in my 1998 Jeep Grand Cherokee which has an automatic transmission and request your opinion of the cause and corrective action. The problem is the torque converter lock-up clutch opens (disengages) momentarily and randomly at steady speed (when above the normal lock-up speed of 45 MPH) on both level and downhill roads and almost always at the bottom of a downhill slope, but I have never noticed this problem on uphill roads. The clutch opens and then immediately re-engages (noted by movement of the tachometer and engine sound). The clutch also opens when the gas pedal is slightly depressed above steady state speed condition. Clutch engagement is delayed above 45 MPH if the vehicle is accelerating which is normal. All other functions of the transmission operate normally. To aid in troubleshooting, I have a question that hopefully you can answer: In addition to road speed and engine speed, what other type(s) of signal (e.g. vacuum, electronic, etc.) and source is required to initiate clutch lock-up and disengagement? Thanks in advance for your consideration and I look forward to receiving your response.