I have a '91 Cadillac 60 Special and the speedometer is numerical and drastiacally fluctuates as I am driving.
57 people viewed your question. They don't know and neither do I. Looks like you need a new speedometer. Get one or you may be getting a lot of tickets in the future. Go to the cadillac parts dept and they will be happy to help you locate one. Pep boys might be able to help you but I'm not positive on the 91.
My guess would be to check your electrical connections on the back of the dash unit....(not easy to get at).
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