2000 Chevy Silverado odometer intermittant

Sometimes the odometer works and sometimes it dosent, not really any pattern to it. When it was colder outside it seemed to not work for about the first 15 minutes in the truck, then work fine- I believe its counting the miles even when not displayed. I am worried because when the odometer display is working the transmission seems to shift fine, but when not displayed it will slip as it shifts into overdrive. Once in overdrive it does not slip. It seems to shift at non-normal times when the odometer is not displayed. All other gauges are working, including the speedometer. The gear indicator goes off when the odometer does, maybe its called "Drive Indicator". Thank you.