Randy mckinney Posted January 26, 2015 Share Posted January 26, 2015 99 RD688s speedo was always about ten mph slow then it quit all together but it still addin miles on odom it has a new ring an sensor any pointers would be great. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/38611-no-speedo/ Share on other sites More sharing options...
turckster Posted January 27, 2015 Share Posted January 27, 2015 Bad speedo head is my first thought. If you have a diagnostic computer w/v-mac3 on it or prolink you should see mph on it. I would think if there was anything wrong you would have a fault and the odometer would not be working. If the mph is still off then the tire rev setting needs to be programmed with correct value. Quote Link to comment https://www.bigmacktrucks.com/topic/38611-no-speedo/#findComment-276189 Share on other sites More sharing options...
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