Well... That all depends...

.4mi high or low? And after how many miles? If it's off by 4/10ths of a mile for every mile, it's REALLY effed up.

You said your speedometer was reading slower than actual speed. If you have smaller tires on the back, it should be reading faster than your actual speed. Maybe someone did a rear end gear swap, or put in a new transmission without properly calibrating the speedometer (happened to me once). Older vehicles need a different speedometer gear. Newer ones need the PCM reprogrammed.

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2011 Ranger XLT 2WD - Dark Shadow Gray Metallic -- SOLD
- Richmond Gear, POWERTRAX No-Slip differential -- FOR SALE
- Advantage, Torza Hard Hat tonneau cover -- FOR SALE
2016 Ford Explorer - Shadow Black
2010 MINI Cooper - "Der Krautenküper"
1993 Special Service Package Mustang - The Five-O's 5-0.

Your speedometer cable could need replaced....it's not like it's 27 years old or anything. lol.

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'01 XLT disguised as a '03 Fx4 Level II.