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i put 4:56 gears in my truck b/c i have 325/60/20 tires on it. now i have a problem with my speedo being off...i have a hypertech programmer to try and adjust the speedo through it but i dont know what i need to set my programmer at. i tried to call hypertech and they couldnt help me out...if any one knows how to find out what i need to set my programmer or how to figure it out please let me know.....thank you
 

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What year truck do you have? Are you saying the speedo was correct until you changed the gears?

The later ones get the speed electronically at the rear diff and it doesn't matter what size gears you have, only the tires. When you change tires on these, the truck must be reprogrammed with the new tire size for an accurate speedo.
 

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dealer can........also latest snap on update can reset pinion correction factor(i think that's what they call it)....can be done to a stock tire size or tire circumference(easily calculated)
 

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I don't have a hypertech programmer but have researched them and they state they can correct the speedometer on a 99. For them you need the tire diameter. The dealer computer would want the revolutions per mile. These vary slightly even on tires that are the same size. You can look up your tire www.tirerack.com or the manufactures's web site to get the diameter or revs/mile.
 
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