My 97 Expedition (189K)recently started having issues. The tach will be reading fine then drop to zero, then work fine again. Sometimes the speedometer will bounce up and down within 5 mph. Now, the OD indicator will start blinking and the transmission will start shifting hard and take longer to shift through the gears. If I turn the ignition off and start it back, everything resets and seems to work fine for a while.
All of these issues have started over the last month. The tach problem happens at any speed, the speedometer happens with no predictible frequency and the transmission issue seems to only happens after 15 plus miles but sometimes it doesnt do it after 100 miles.
Somedays and on short drives, there doesnt seem to be anything wrong at all.