Speedometer
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Joined: Aug 1999
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Speedometer
I have a 96' Ranger the truck came stock with P215/75/R15 tires. I have replaced them with 31x10.5's. I was wondering if the speedometer is computer controlled, rather than gear driven for a better word? I'm not sure if it is reading the correct speed and when I've done the calculation (old tire diameter divided by new tire diameter multiplied by curent speedometer reading= Actual speed) It does not seem remotely correct. For instance while driving down the freeway my speedometer reads 70MPH and the speedlimit is 70MPH but it seems like I'm passing everybody...am I going faster or is everybody else just driving extremly slower than the speed limit. By my calculations by the way, If the speedometer says im doing 70 then I should actually be going 60/61 MPH. I totaly contradict the formula because I feel as though I'm going faster than the speedometer registers not slower.....HELP!!!!!!!
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Speedometer
I have a '94 Ranger 4x4 with the 4.0 motor. My truck had a gear swap, so now it runs 4.56 gears, and I have 31x10.5 all terrain tires. The gear change really threw off the speedometer, by a wide margin. I took the truck to a speedo shop and they ran it on their dynometer (or whatever that contraption was) and then wound up replacing a gear of some sort in the transmission. They kept the gear that they removed; I guess it's an exchange deal or something. The whole process cost me approximately $100 if I recall correctly. But, they got the speedo to read almost exactly what it should be reading.
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Joined: Jun 1999
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Speedometer
No offense but you are thinking backwards on this. You see,when you install larger diameter tires,the speed of the driveshaft is slower with the same foward speed of the truck itself.Therefore,the speedometer will also be slower{less indicated forward speed}also.I will say you are correct about the percentage difference,but,you need to add the percentage to what you see at the speedometer.For example,the larger tire netted a 10% increase:60mph x 10%=6mph.Then 60mph 6mph = 66mph.When your speedo marks 60mph,you are actually moving forward at 66mph.This is why you are going faster than everybody else.
Phillip
Phillip
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Joined: Dec 2001
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From: South Jersey
Speedometer
You are going faster than the speedometer. I'm not sure which year Ford changed to an electonic speedometer but you can just check for a cable. If you have a cable all you need to do is change the gear, cheap and easy, no cable you need a scanner to change the calibration. If you need the procedure I can email it to you.
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Jonnys.1991
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