Zeus - get that problem up here in cold country all the time. When the car is cold the needle bounces all over the place and you can hear the chatter. Real bad at -20 to -30 outside. As the car warms up the speedo starts to work normally. Problem does not occur when it gets warmer out. Solution: Pull the speedo cable out of it's sheath and wipe it clean with solvent. Liberally cover it with white grease (or if you have it - speedo lube) and re-insert it back into the sheath. Usually lasts for about 2 years before it needs fresh cleaning and lubing up here. On the bright side - when the needle is bouncing all over the place you can at least see what it looks like at 145 mph!!!