tires, speedometers, and programmers
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Freshman User
Joined: Aug 2005
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From: Griswold, CT
tires, speedometers, and programmers
I'm new to the site, and this is my first post - I hope I chose the correct forum (I debated which one to use for about 5 mins).
Here's the issue: 2002, F350 SRW, 7.3L. Had 275 75R16 until today. After a lot of reading on this fine site, and problems getting in and out of hunting areas, put on BFG AT KO 285 75R16 today.
I hunt (therefore drive in SC red clay) 3 times a week, I tow horses (trailer weighs about 5k), and use the truck to move hay frequently.
Previously, the speedometer was 5.5 mph fast (therefore racking up the miles too fast as well). Now, I think it is closer to correct, but I would like it to know it is correct.
I know about the Superchips TrueSpeed (I think that's the name). But it's a little pricey considering it only does the speedometer. I've talked to every dealer within an hour and NONE will recalibrate the speedometer.
I'm looking at the Diablo Predator and have not been able to figure out if that product will recalibrate my speedometer. Any suggestions? I'm sending them an email to ask this question as well. I hope to hear the Predator will do what I want to help fuel mileage and power!
Last bit - does anyone think there is a better programmer (not chip) for me?
Here's the issue: 2002, F350 SRW, 7.3L. Had 275 75R16 until today. After a lot of reading on this fine site, and problems getting in and out of hunting areas, put on BFG AT KO 285 75R16 today.
I hunt (therefore drive in SC red clay) 3 times a week, I tow horses (trailer weighs about 5k), and use the truck to move hay frequently.
Previously, the speedometer was 5.5 mph fast (therefore racking up the miles too fast as well). Now, I think it is closer to correct, but I would like it to know it is correct.
I know about the Superchips TrueSpeed (I think that's the name). But it's a little pricey considering it only does the speedometer. I've talked to every dealer within an hour and NONE will recalibrate the speedometer.
I'm looking at the Diablo Predator and have not been able to figure out if that product will recalibrate my speedometer. Any suggestions? I'm sending them an email to ask this question as well. I hope to hear the Predator will do what I want to help fuel mileage and power!
Last bit - does anyone think there is a better programmer (not chip) for me?
Last edited by sawfish99; Aug 29, 2005 at 10:36 PM.
Postmaster
Joined: Nov 2004
Posts: 2,854
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From: New Hampshire
send them an email.. i thought that the predator that i bought would do more than it actually does, although i have not really researched it... i am going to contact them and ask some questions... i do like the way the programer has brought my motor to life, stock just sucks... there is sooooo much more power in that engine...!
Elder User
Joined: Feb 2004
Posts: 907
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From: West Haven, UT
From what I have read/heard, the Predator does not recalibrate the speedo. This worked on my truck (97 F250) but I don't know if it will work on your truck but there is a procedure I got from here (Baz's page)
There is no tire size/code chart because tire size vs. actual tire dimensions are different between manufacturers. Even between the same tire size and same maker there will be a difference in actual size between the different tread designs.
The Ford calibration equation is:
20186 / tire height in inches = some number, then: some number /.6666 = program code
Example:
Start with 20186, divide by actual tire size in inches. Divide again by .6666
You want to use a rolling measurement to get your actual tire height (If you try to measure the tire in the driveway, use conversion charts, or anything else you will end up with an inaccurate reading again). Use your rear tire since the sensor is located there. Mark the ground and your tire and roll forward 3 times marking the ground each time. (I ran over a spot of oil at a local gas station and measured between my tread mark prints), then divide that number by three to get the average length of one revolution (this will protect yourself against a bad reading using just one revolution). You can then divide the length of one revolution by 3.14 to get actual tire height. Be careful in your measurements, a small amount will change the code. EX: 31.69" tire height is code 956, and 31.21" tire height is code 970.
Now, to program it into your truck:
Warning: You can only change the calibration 6 times without replacing the module.
To set the calibration, ground the single wire connector under the glove box it says PSOM (Programable Speedometer Opdometer Module). ”Yes there is only one and it has a spade type plug on the end". I used a wire with clips on both ends to ground the plug to a screw under the dash or try a test light and use the clip end to the PSOM and the other jam in a dooe hinge. Now look at your speedometer on the face of your dash while sitting in the drivers seat and there should be a "reset" button and a "select" button. While holding the reset button in on the trip meter, turn the ignition to 'on' while the wire is still grounded. Let go of the reset button. The speedometer display will sweep once and will show a code of some kind then push in again the "reset" button and the existing code will be displayed with RECAL?, mine said 976 RECAL? Now you enter your new code you came up with by dividing the rolling measurement by PI or 3.14 by pushing the "select" button until it gets to the new calibration code number. You may have to push “select” a whole bunch of times until you get to your code. If you turn off the key at this point the original code will not be changed or any of the 6 lives will not be used. To store your new code press “Reset”. Turn off the key. Unplug the ground wire. To check the new calibration, use the mile markers on the interstate. Run an indicated 60 mph and it should take exactly 60 seconds to go 1 mile.
The Ford calibration equation is:
20186 / tire height in inches = some number, then: some number /.6666 = program code
Example:
Start with 20186, divide by actual tire size in inches. Divide again by .6666
You want to use a rolling measurement to get your actual tire height (If you try to measure the tire in the driveway, use conversion charts, or anything else you will end up with an inaccurate reading again). Use your rear tire since the sensor is located there. Mark the ground and your tire and roll forward 3 times marking the ground each time. (I ran over a spot of oil at a local gas station and measured between my tread mark prints), then divide that number by three to get the average length of one revolution (this will protect yourself against a bad reading using just one revolution). You can then divide the length of one revolution by 3.14 to get actual tire height. Be careful in your measurements, a small amount will change the code. EX: 31.69" tire height is code 956, and 31.21" tire height is code 970.
Now, to program it into your truck:
Warning: You can only change the calibration 6 times without replacing the module.
To set the calibration, ground the single wire connector under the glove box it says PSOM (Programable Speedometer Opdometer Module). ”Yes there is only one and it has a spade type plug on the end". I used a wire with clips on both ends to ground the plug to a screw under the dash or try a test light and use the clip end to the PSOM and the other jam in a dooe hinge. Now look at your speedometer on the face of your dash while sitting in the drivers seat and there should be a "reset" button and a "select" button. While holding the reset button in on the trip meter, turn the ignition to 'on' while the wire is still grounded. Let go of the reset button. The speedometer display will sweep once and will show a code of some kind then push in again the "reset" button and the existing code will be displayed with RECAL?, mine said 976 RECAL? Now you enter your new code you came up with by dividing the rolling measurement by PI or 3.14 by pushing the "select" button until it gets to the new calibration code number. You may have to push “select” a whole bunch of times until you get to your code. If you turn off the key at this point the original code will not be changed or any of the 6 lives will not be used. To store your new code press “Reset”. Turn off the key. Unplug the ground wire. To check the new calibration, use the mile markers on the interstate. Run an indicated 60 mph and it should take exactly 60 seconds to go 1 mile.
Postmaster
Joined: Jul 2004
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From: Yuba City, CA.
That procedure is for the Old body style (OBS) trucks only I believe. I was tiold that the dealer was able to recalculate the speedo. Superlifts Tru Speed is a good product, I don't have one though. You should be racking up less actual miles if you have bigger than stock tires. Are you the original owner of the truck? The reason I ask is because maybe it was already calibrated for bigger tires and someone put smaller ones back on.
Thread Starter
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Freshman User
Joined: Aug 2005
Posts: 45
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From: Griswold, CT
Originally Posted by WA.Ranger
That procedure is for the Old body style (OBS) trucks only I believe. I was tiold that the dealer was able to recalculate the speedo. Superlifts Tru Speed is a good product, I don't have one though. You should be racking up less actual miles if you have bigger than stock tires. Are you the original owner of the truck? The reason I ask is because maybe it was already calibrated for bigger tires and someone put smaller ones back on.
NONE of the dealers in my area admit to having the ability to correct the problem. I think the new tires have come close to correcting the difference.
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Elder User
Joined: Feb 2000
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From: LAKE FORK TEXAS
Every truck is different,but with my 02 F350 and Stock tires (265's) My speedo was about 2-3 mph fast, now with the 285's it is exactly the same as the 4 different GPS units i have checked it with.
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I remember seeing a few years back someone posted the instuctions for recalibrating the speedo on an 99- SD. It was done with a plug in computer, the service writers I recall could do this. I recall the lowest setting was in revs per mile and it was about 606 or something. I'm trying to dig that up.
I also went to a dealer last night and he had no knowledge of this. I'm sure I remember this but didn't save it. The dealer recommended a tru speed or chip. I don't want to spend $200 for a truspeed or 400 for a chip. I'm still digging but would appreciate if anyone else remembers this or has heard of it.
Thanks,
Rob
I also went to a dealer last night and he had no knowledge of this. I'm sure I remember this but didn't save it. The dealer recommended a tru speed or chip. I don't want to spend $200 for a truspeed or 400 for a chip. I'm still digging but would appreciate if anyone else remembers this or has heard of it.
Thanks,
Rob
Senior User
Joined: Apr 2000
Posts: 158
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Found it, now to find a dealer willing to do it...
Special Service Message 11789 & 11790 from 7/29/99.
1)Ensure all harness connections are plugged in.
2)Using Rotunda New Generation Star (NGS) scanner and Version 3.2 or higher Service Card, Plug into the DCL connector. [ADDED: Do not use a service card version later than early 2001 model year. This will not work if you try to use a service card dated after the 2002 models came out. But it will work on 2002 or earlier trucks if you use a Service Card for 2001 or earlier SuperDuties.]
3)Turn Key on w/Engine Off.
4)Select Service Bay Functions
5)Select ABS Module or 4WABS Module depending on application.
6)Select Tire Size/Axle Ratio Configure.
7)Enter tire manufacturer's specification of revs/mile (tire revolutions per mile). If not available, use Formula of: 63360 Divided by the Circumfrence of the tire measured in inches. Add 2 zeros in front of the solution. Enter this number into the NGS as the REV.PER MILE figure.
[ADDED: To be even more accurate, enter the following rev/mile:
For 285/75R16 tires enter 00636
For 295/75R16 tires enter 00626
For 315/75R16 tires enter 00601
Do not try to enter a number less than 00601.]
8)Select Tone Ring size and verify that 120 is programmed in.
9)Select <Option> and press TRIGGER.
10)Select <Vehicle> and press TRIGGER.
11)Press <Done> and the Module will be reprogrammed.
12)Check Speedo accuracy.
Special Service Message 11789 & 11790 from 7/29/99.
1)Ensure all harness connections are plugged in.
2)Using Rotunda New Generation Star (NGS) scanner and Version 3.2 or higher Service Card, Plug into the DCL connector. [ADDED: Do not use a service card version later than early 2001 model year. This will not work if you try to use a service card dated after the 2002 models came out. But it will work on 2002 or earlier trucks if you use a Service Card for 2001 or earlier SuperDuties.]
3)Turn Key on w/Engine Off.
4)Select Service Bay Functions
5)Select ABS Module or 4WABS Module depending on application.
6)Select Tire Size/Axle Ratio Configure.
7)Enter tire manufacturer's specification of revs/mile (tire revolutions per mile). If not available, use Formula of: 63360 Divided by the Circumfrence of the tire measured in inches. Add 2 zeros in front of the solution. Enter this number into the NGS as the REV.PER MILE figure.
[ADDED: To be even more accurate, enter the following rev/mile:
For 285/75R16 tires enter 00636
For 295/75R16 tires enter 00626
For 315/75R16 tires enter 00601
Do not try to enter a number less than 00601.]
8)Select Tone Ring size and verify that 120 is programmed in.
9)Select <Option> and press TRIGGER.
10)Select <Vehicle> and press TRIGGER.
11)Press <Done> and the Module will be reprogrammed.
12)Check Speedo accuracy.
