The last few weeks the speedometer has had a mind of it's own, sticking up, then it finally drops. This week nothing , so I pull the cluster and the cable is broken. MY qwestion is did speedometer malfunction kill the cable? I cut off the tip of the cable and stuck it in the speedometer and spun it, spins freely and registers. If the cable was fatigued and broke why was the speedometer acting up for a week???

Outside temp 45 deg

Thanks in advance

__________________
1983 300 D 256K Turbo drain, vacuum pump