Hey I have a 97 f-150 4x4 ORP and 35" tires. i just changed my gears. when i had 3.55 gears i would actually be going faster down the highway than what the spedometer said.Now i have 4.56 gears and it seems that i am now going slower than the spedometer says . So my question is how can i determine if it is off and then how to and how much to adjust the spedometer or will i have to take it to a mechanic. Any advice will be appreciated .

Thanks
Bigern

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The ORP tires are 31.5" and you now have 35". You had 3.55's and now 4.56's. It is a matter of ratios:

(31.5/35)*(4.56/3.55) = 1.16 - so your speedo is 16% high now.

You can correct this with a new VSS gear - increase the number of teeth by 16%. If you have 19 teeth now, you will need 19*1.16 = 22 teeth.

Ian

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99 Expedition EB
5.4l, 4x4, 4.10 LS
WMS Tube, Bassani Cat Back Exhaust, Superchip Flipchip, PIAA Superwhites

 

Hey Ian N
Thanks for the response i really appreciate it. but now where can i get that VSS gear with 22 teeth? that is if i have a 19 tooth gear. and where is this gear located on my truck and is it hard to change. And thanks again Ian N.

Bigern

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[This message has been edited by Bigern6697 (edited 05-18-2001).]