Speedometer does not go over forty mph no matter how fast I am going

1999 FORD F-250
250,000 MILES • 5.4L • V8 • 4WD • AUTOMATIC
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KEITHW71
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This a SD truck. The speedometer goes up to 40 mph and stops there regardless of how fast you are really going. It is correct up to 40. I have replaced the sensor in the rear end. no change.,Also, transmission shifts a little funny and in overdrive feels like it is hopping. Please help. Thanks
Feb 20, 2019 at 8:55 AM
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MPNANTO
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Hi Keith,

Thanks for visiting 2CarPros.

I have a couple of quick questions, with the speedometer inoperable does the odometer still work?

Does the vehicle have any misfires? Coils can cause a speedometer failure.

When you measure A/C voltage across the OSS is it climbing as you increase speed?
Feb 20, 2019 at 6:29 PM
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KEITHW71
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No misfire, speedometer works up to 40 mph then won't climb pass that, just stays at 40.
Feb 20, 2019 at 6:44 PM
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MPNANTO
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Are you able to set the cruise control over 40?

Can you read A/C voltage at the sensor when the vehicle is going over 40 MPH?
Feb 20, 2019 at 9:26 PM