I no longer have this vehicle, but this question has been a mystery to anyone I asked, and I don’t have an answer. I had a 1977 Chevy 1/2 ton pickup with automatic transmission and 4wd. It was equipped with an in-dash LED clock that never kept good time. One day without warning, the front u-joint on the front driveshaft disintegrated and tore through the yoke. It would take a few days for the parts store to get a new shaft, so I drove the truck without it. During that time, the clock kept perfect time. After I installed the new driveshaft the clock went haywire again. Why?
Not a clue but, I wonder if the clock was sensative to some magnetic field interference from the position of the drive shaft in proximity to the clock ??
Perhaps the driveshaft is causing a vibration that’s affecting a flakey clock connection.