MAP Posted April 28, 2007 Report Share Posted April 28, 2007 I intend to put 4.10s in my car (#687), but I am not sure on how to get the speedometer corrected. In the past on the older new Mustangs I have either had a hand held programmer to do it or used a Speedcal from Dallas Mustangs. I called Dallas Mustangs and they said they have never tried a Speedcal on a newer car and were not sure if it would work. Also with the Shelby program already installed I figure hand held programmer might not work either. Does anyone have any experience or advice on this? Thanks Mark Potter Link to comment Share on other sites More sharing options...
dmagner1 Posted April 29, 2007 Report Share Posted April 29, 2007 the computer of the car will correct it self Link to comment Share on other sites More sharing options...
csm198 Posted April 29, 2007 Report Share Posted April 29, 2007 the computer of the car will correct it self I just rode back from shelby and my sppedometer said 80 but my gps said 75. Im not sure what to believe Link to comment Share on other sites More sharing options...
SAI-John Posted April 30, 2007 Report Share Posted April 30, 2007 To go to a 4.10 ratio would require a recal of the computer. The SGT comes with a 3.55. I could see maybe wanting a 3.73, but a 4.10? What are you going to be using your car for? -John Link to comment Share on other sites More sharing options...
MAP Posted April 30, 2007 Author Report Share Posted April 30, 2007 To go to a 4.10 ratio would require a recal of the computer. The SGT comes with a 3.55. I could see maybe wanting a 3.73, but a 4.10? What are you going to be using your car for? -John I have used 4.10s with great results in my 98 Cobra and my first Bullitt, this is a great gear for just about anything you want to do, the cars really wake up with these. I don't think a 3.73 would be enough of a difference to be worth the trouble( unless I had an auto). On both the Cobra and Bullitt I saw a decrease of about 1-2 mpg, and this SGT gets really good mileage anyway, so I am willing to take the loss. Back to the computer, just who can do the recal seeing as the program installed is non stock? What would you recommend ? ( not why, but how) Thanks Mark Link to comment Share on other sites More sharing options...
mark1 Posted April 30, 2007 Report Share Posted April 30, 2007 I just rode back from shelby and my sppedometer said 80 but my gps said 75. Im not sure what to believe My SGT feels like it is also off by about 5mph. I have not done any testing yet to verify. Do the SGTs get recalibrated for the 355's? Do they require it? DMAG stated it should happen automatically but I don't see how that could be the case. How would the computer be aware of a gear ratio different from stock 323? I assume that the manual trans 355's installed at the factory in Flat Rock would be recal'ed there and the auto trans like mine would be done at SAI. Can John or Bud shed some light on this subject? Thanks, Mark Link to comment Share on other sites More sharing options...
DreamRide Posted May 2, 2007 Report Share Posted May 2, 2007 My SGT feels like it is also off by about 5mph. I have not done any testing yet to verify. Do the SGTs get recalibrated for the 355's? Do they require it? DMAG stated it should happen automatically but I don't see how that could be the case. How would the computer be aware of a gear ratio different from stock 323? I assume that the manual trans 355's installed at the factory in Flat Rock would be recal'ed there and the auto trans like mine would be done at SAI. Can John or Bud shed some light on this subject? Thanks, Mark You will need a hand held tuner or the likes to change the speedo. It does not change itself. I had another S197 mustang that i traded in for my shelby and i had an SCT tuner for it with custome tunes. With it i was able to change many perameters and one of them was gear ratio and tire size to correct the speedo. Link to comment Share on other sites More sharing options...
MAP Posted May 2, 2007 Author Report Share Posted May 2, 2007 I think I am on the right track I talked to the tech. line at Ford Racing Parts this morning. They said they could send me a device that would reflash the system and correct for the 4.10 gears. The cost is $80 plus a $150 core deposit that is refunded when they get their box back. These will be available next week. I have gears coming so in a couple of weeks I will give it a try. Also the guy at Ford said not to try and drive the car with the incorrect calibration in the computer ( he didn't say what the results would be however), so this whole process will take some planning to get done all at once. Mark #687 Link to comment Share on other sites More sharing options...
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