Speedometer off by two mph

1999 GMC C1500
200 MILES • 5.2L • V8 • 2WD • AUTOMATIC
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WHITEY93193
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Speedometer off by two mph when reaching fifty mph or greater.
Engine new, transmission has 156,000 miles on it.
Runs and drives great.
Twenty five gallon gas tank, only getting thirteen mpg. Should be better.
Van is a 1999 unclean Savannah 2500 cargo.
Jan 17, 2018 at 10:50 PM
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STEVE W.
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That is well withing the tolerance of tire sizes specified for that van. You can take ten different tires with the same sizes on them and when installed and inflated they will measure slightly different in actual diameter depending on the tread style, depth, tire construction and rubber compounds. Even something like changing the inflation pressure by a few pounds will alter the actual ground speed.

Thirteen mpg is about normal for a van of that time. They are a work truck so the gearing and transmission are designed for weight not mileage.
Jan 18, 2018 at 12:17 AM