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

Tiny
KEITHW71
  • MEMBER
  • 1999 FORD F-250
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 250,000 MILES
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
Wednesday, February 20th, 2019 AT 8:55 AM

3 Replies

Tiny
MPNANTO
  • MECHANIC
  • 17 POSTS
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?
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Wednesday, February 20th, 2019 AT 6:29 PM
Tiny
KEITHW71
  • MEMBER
  • 5 POSTS
No misfire, speedometer works up to 40 mph then won't climb pass that, just stays at 40.
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Wednesday, February 20th, 2019 AT 6:44 PM
Tiny
MPNANTO
  • MECHANIC
  • 17 POSTS
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?
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Wednesday, February 20th, 2019 AT 9:26 PM

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