Re: speedometer jumping at high speeds help
Most likely a dry, kinked or otherwise damaged cable. You could try lubing it but don't overdo it or the lubricant will migrate into the cluster.
Also could be a problem with the small plastic gear where the cable/speed sensor plugs into the transmission.
Possibly the speedometer itself but I would keep that at the bottom of the list.
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid