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Run down I have 2010 Crew Max 4x4 installed 4.5 bds lift w/35x12.5r20 nitto trail grapplers & regeared to 4.88 front and rear diffs. Installed a hypertech speedo cal thought I had my numbers correct but No.
Here is what I have for numbers:
First number is what I am seeing on the speedo second number is the gps reading.
35=38.4 mph
40=45.1 mph
50=55.6 mph
55=60.6 mph
60=66.6 mph
65=72.7 mph
70=78.7mph
How the heck do I correct this.Hypertech states only put the tire in inches in there software not the tire sizes and don't put the new gear ratios in Please assit Thank you
 

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I'm pretty sure u have to put in the gear ratios. Did u call hypertech and ask a tech?
 

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Doesn't the combination of 4.88 gears and 35" tires get the final ratio back to almost stock? I would say you need to do some math and figure out exactly how a 31" tire with 4.30 ratio compares to a 35" tire with a 4.88 ratio


Edit: looks like that combo of gear ratios and tires will only result in your speedo being off by 0.5% percent. long story short you don't need a calibrator at all
 

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I wouldn't mess with the tire size and gearing changes in the software. The calibrator just uses a % difference conversion. Reset the unit back to factory and drive a few days to find out what % you are off from stock. (The best speed to check is with speedo reading 50 mph and multiply GPS reading by 2. that will be your % you are off. The numbers you have listed are after some kind of adjustments have already been made. They show a positive difference and it should be negative with 4.88's and 35's.

The numbers you listed You're showing roughly + 11%. If this was stock + 11% you would just need to open the software, choose changed gear ratio. Old gear ratio = 1:1. New gear ratio = 1.11:1. It would show a conversion factor of .9009 then you would just have to program and be finished.

The problem is you're + 11% over what you currently have it set for not + 11% over stock gearing. If you know what you had already put in the math could be done to figure it out but that's a little more difficult.

I'm going to bet it you put in old gear = 1 and new gear = .9577 it will give conversion factor will be 1.044 and speedo should be fairly close.



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