Mustang, 1965–1985
Classic Mustangs used a cable-driven speedometer throughout the era, from the 1965–1973 clusters through the 1979–1985 Fox-body. The most common complaint is the familiar dry-cable bouncing needle at low speed — clean and lubricate the cable before anything else. A lazy, sticking or dead needle with a good cable points to hardened grease in the gauge head and a bench rebuild.
Reads wrong after a rear-end or tyre change
Mustangs are heavily modified, and a speedo that reads high or low almost always means the driven gear at the transmission no longer matches the tyre diameter and axle ratio. Fit the correct driven gear for your combination, or have the gauge recalibrated to the right turns-per-mile. This is calibration, not a mechanism fault.
F-series & Bronco trucks
Ford trucks share the same cable-drive architecture, but longer cable runs and tighter routing make binding and “whip” more common — keep the cable short, sweep the bends, and lubricate with graphite or PTFE. A stripped plastic drive gear at the transmission is a frequent cause of a dead speedo on high-mileage trucks.