1984 Saab 900 speedometer problem

My speedometer stopped working, or rather it worked intermittently and now has stopped altogether. The last time it worked was after I hit a big bump on the road and it abruptly came back for a couple hundred miles but stopped again. I disconnected the speedometer cable and lubed it and tried to spray some lube in the back of the speedometer as well. It worked for a while and has stopped again. The cable itself seems to be fine as the odometer is working correctly. Does anyone have an idea what's going on? I know with the odometer there is a gear that slides out of mesh with another gear and that's what seems like going here as well, but I don't know the inner workings of the speedometer. Taking it out seems to be a big pain in the butt, so I didn't want to take it out unless there is an easy fix or at least one I can do myself. Otherwise, I'll live with no speedometer, like on most of the Alfa Romeos I have!