speedometer recalibration
Member
Joined: Mar 2000
Posts: 34
Likes: 0
From: Willis, MI
I upsized my tires from 245/75R16 to 285/75R16 and noticed a 5 mph difference in the speedometer, used a Garmin GPS III+ to verify the speeds. I talked to 2 different dealers here in the Dayton, OH area and the 2nd dealer informed me about a VSS (Vehicle Speed Sensor) located at the rear of the transmission. The VSS spends the transmission tailshaft RPM data to the PCM (Powertrain Control Module) and the PCM sends, among other things, a signal to the speedometer.
What all this means is, change the gear on the end of the VSS and it will correct the speedometer error. Get a Haynes manual for your truck, it shows (Page 6-10) a good reference picture of the VSS.
Remember if your speedometer is reading low (indicates 50, actually doing 55) get a gear with less teeth, if your speedometer is reading high (indicates 55, actually doing 50) get a gear with more teeth. 1 tooth = 5 mph. My truck originally had a 20R (20 teeth R/H spiral) gear. Since my speedometer was 5 mph low I got a 19R gear. The VSS is very easy to get to, 1 10mm nut holds it on and 1 electrical connector.
Also the "R" in 20R and 19R stands for R/H. When you remove the VSS the gear is held on by a small clip, remove the clip and place the gear on the table, shaft up. Look at the teeth from the side, if the end of the tooth at the top is to the RIGHT of the end of the same tooth at the bottom, you have an "R".
Hope this helps. The gear is a lot cheaper than a new set of tires. I got lucky, a mechanic at the dealer I went to had changed his tires and taken out a 19R, I got mine for free. I don't think the gear would be more than $20-30.
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1997 F-250 Light Duty, Super Cab, Short Bed, 5.4L, 4x4, Gibson SuperTruck exhaust, K&N Filter, BFG AT(KO) 285/75R16, Westin Black Nerf Bars, SuperChip. West Milton (Dayton), OH
What all this means is, change the gear on the end of the VSS and it will correct the speedometer error. Get a Haynes manual for your truck, it shows (Page 6-10) a good reference picture of the VSS.
Remember if your speedometer is reading low (indicates 50, actually doing 55) get a gear with less teeth, if your speedometer is reading high (indicates 55, actually doing 50) get a gear with more teeth. 1 tooth = 5 mph. My truck originally had a 20R (20 teeth R/H spiral) gear. Since my speedometer was 5 mph low I got a 19R gear. The VSS is very easy to get to, 1 10mm nut holds it on and 1 electrical connector.
Also the "R" in 20R and 19R stands for R/H. When you remove the VSS the gear is held on by a small clip, remove the clip and place the gear on the table, shaft up. Look at the teeth from the side, if the end of the tooth at the top is to the RIGHT of the end of the same tooth at the bottom, you have an "R".
Hope this helps. The gear is a lot cheaper than a new set of tires. I got lucky, a mechanic at the dealer I went to had changed his tires and taken out a 19R, I got mine for free. I don't think the gear would be more than $20-30.
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1997 F-250 Light Duty, Super Cab, Short Bed, 5.4L, 4x4, Gibson SuperTruck exhaust, K&N Filter, BFG AT(KO) 285/75R16, Westin Black Nerf Bars, SuperChip. West Milton (Dayton), OH
Member
Joined: Feb 2000
Posts: 24
Likes: 0
From: Bloomsburg, PA, USA
Do a search in the forums. I believe that with the 2000, it's not a gear change, but a program calibration.
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2000 XLT SC 4x4
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On Order Since 2/10/00
2000 XLT SC 4x4
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Member
Joined: Mar 2000
Posts: 34
Likes: 0
From: Willis, MI
Your right, I missed the "2k" in the post, my mistake. You can go to Ford for computer (speedometer) recalibration or check the chip manufacturers for a programmer.
Hypertech: http://www.hypertech-inc.com/main.html
Jet: http://www.jetchip.com/
Superchip: http://www.superchips.com/
With my 97 it was a gear on the VSS. I believe Ford swapped to the computer in 99.
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1997 F-250 Light Duty, Super Cab, Short Bed, 5.4L, 4x4, 3.73LS Gibson SuperTruck exhaust, K&N Filter, BFG AT(KO) 285/75R16, Westin Black Nerf Bars, SuperChip.
Hypertech: http://www.hypertech-inc.com/main.html
Jet: http://www.jetchip.com/
Superchip: http://www.superchips.com/
With my 97 it was a gear on the VSS. I believe Ford swapped to the computer in 99.
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1997 F-250 Light Duty, Super Cab, Short Bed, 5.4L, 4x4, 3.73LS Gibson SuperTruck exhaust, K&N Filter, BFG AT(KO) 285/75R16, Westin Black Nerf Bars, SuperChip.