Well, it could be something as simple as a speedometer cable. There is a cable that runs from the back of the speedo to the transmission. They fail on older vehicles a lot. GM's instrument clusters are known to have troubles too. The cable can be purchased from the local parts store. Pick one up and with a little creativity you could add it to the Valentines gift for him. Tuck it under a cute set of boxers and throw in a Home Depot gift card. Don't say anything....guys can always turn a simple request into a nagging situation. The cable will say it all.
If the cable doesn't fix the trouble then take it to a speedometer shop in your area.
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