speedo & mileage

[BakerEdition]

took the old girl for a ride today to get the cob webs out...speedo is off but + or - 3 mph is pretty average for a production speedo..but its the fuel mileage that has me very pleased..

 

[Milwaukee]

I have my 99 Expedition at dealership 2 days ago for recalibration to match tire size due previous owner put smaller tires so it been rack up alot miles than actual.

What I notice that speedometer and RPM aren't accurate if you watch closely it tick not freely moving.

I check mine with GPS and scangauge they were 1 mph off it perfect but speedometer read 2-3 mph off.

Just check your GPS with your edge see if speed are same. Just ignore speedometer. I think they doesn't work well when age/mile on it.

 

[BakerEdition]

i have nav gps on the radio and everthing matches but the speedo...on police cars the speedometer is "certified calibration" meaning they are not production, they are person checked at a bench an ca not be more than + or - 1mph or replaced. I wish i could send the cluster to someone for calibration.

 

[Milwaukee]

i have nav gps on the radio and everthing matches but the speedo...on police cars the speedometer is "certified calibration" meaning they are not production, they are person checked at a bench an ca not be more than + or - 1mph or replaced. I wish i could send the cluster to someone for calibration.

Don't you work at police station? I am sure they have someone there to able do recalibration your speedometer with their equipments?

 

[Thermo]

Chappy, if you want your speedo calibrated, it is pretty simple. Get out on the highway and set the truck at a given speed (I use 60 mph as it is easy, but you can do it at 70 mph too, probably recommended to do it at the speed that you tend to normally drive). now, find a fairly flat stretch of road that has milemarkers and where you don't have to change speed. Set the cruise and as you pass a milemarker, start a stop watch (I use my wrist watch). Drive say 5 miles and as you pass that last mile marker, stop the stop watch. Convert the time to seconds. Divide the time into 3600 and the multiply by the number of miles you drove. You now have the average speed that you drove. Since you had the cruise set, it should be what the speedo was reading unless you were hitting some decent hills. From there, you can ratio what you calculated by what your speedo read. You should get a number like 1.01. This would mean your speedo is off by 1% (subtract 1 and then multiply the decimal by 100). From there, you can take the truck to any dealership (some shops can even do it) and tell them that you need your ECM recalibrated and the "Revs/mile" updated in the computer to correct for the XX% error in the speedo. They do a little calculation and you are golden.