I have a 86 silverado and the transmission vacuum line is attached to the intake manifold near the number 8 cylinder. Is yours like that? It could be a ruptered diaphram in the vacuum modulator and getting sucked in the intake and going to the cylinder(transmission fluid).
Sitting at an idle or while driving, the oil gauge will flicker alittle bit. Has anybody ran into this before and found the fix. I have a wiring diagram for the truck and trying to trace all the wiring. It is a 86 chevy silverado k20 with stock gauges. Any help would be appreciated.