Speedometer drops down on its own when driving

2007 HUMMER H3
160,000 MILES • AUTOMATIC
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WIFEH3OWNER
  • MEMBER
  • 1 POST
Hi

My husbands vehicle about three weeks ago got a new transmission replaced. Three days ago while driving on the highway doing about eighty mph when the truck on its own dropped down its speed to about fifty mph. It is shifts up and down on its own. The mechanic that replaced the transmission has no ideal what is going on.

Please say you can give us some direction!

Thanks

A wife of a H3 owner.
Aug 10, 2018 at 7:46 PM
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STRAILER
  • ✓Experienced Mechanic
  • 55,561 POSTS
Hello,

This sounds like the vehicle speed sensor is having an issue. But to be sure lets run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

Cheers, Ken
Aug 13, 2018 at 7:10 AM
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