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speedometer is slow with no changes

818 Views 5 Replies 2 Participants Last post by  to4tz
1991 - my speedometer has become slow on it's on with no changes made to the truck. It ranges from 12 to 15 mph slow depending on your speed. I have checked it with a Garmin GPS to verify. I replaced the instrument cluster with a working used unit 2 years ago and checked it at that time with GPS and it was spot on. Any ideas on what is going on?
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Ok - Thanks will check it out :thanks2:
Slow speedometer

I pulled the plastic gear on the transmission and it looked fine. Also cleaned out the speed sensor and still have the same problem. Next I replaced the speed sensor and still same problem. To me it is looking like the speedometer itself has the problem. Could it be faulty electronic components?

Ok, I will take a look at the speedometer next. Thanks
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