My question is. I have a stock 97 f150 with 3.55 gears and 255-70-16. I just put in 4.56 gears and put on 315-75-16 (35") bfg tires. my speedometer is slow about 4 mph, not a big deal but i would like to get it right on the money. Has anyone change the speedometer gear on a 97 f150 and if so how hard is it? Also where can i get it from? I would just take it in to the shop, but they said it was 85.00 plus parts. which sounds like a rip off to me.

 

New gears can be gotten from ford, provided one from a stock setup would work in your application. You need to find out what % your speedo is off and use that figure out how many teeth different you need. The fewer the teeth the faster the speedo will turn (corrects a slow problem like you have), more teeth make it turn slower. Gears from Ford cost about $10, and it takes about 2 min to change the gear. $85 is robbery.

 

where is the gear located?

 

Drivers side of the tailshaft housing on the transfer case if its a 4x4. Same place on the transmission if its a 4x2.

 

In searching for recalibration of the speedometer for my 97 F150 4x4 I came accross the site listed below. Is what they say about all the onboard computers and mis-information accurate?
http://www.4wheelerssupply.com/catal...oducts_id/1762

I have used several calculators on the web and I found that my speedometer is about 10% slower than the actual speed. So I need to figure out how many teeth the current gear has and get one with 10% fewer teeth?

 

First, take a drive down the freeway. Stop next to a mile marker on the freeway, reset the odometer, then drive 10 miles (at whatever legal speed necessary) and stop next to that mile marker. Your speedo will read something around 10 miles. Divide the odometer's measurement by 10 and you'll get a number. Take that number and multiply it by the number of teeth on your current speedo gear, and that'll tell you the exact number of teeth you want the gear to have. Obviously you won't find a gear with XX.yyy teeth, so you'll need to round it up or down. If you're right in the middle, rounding up will run the speedo a bit slow, rounding down will run the speedo a bit fast. Pick your poison.

Example: You drive 10 miles and the odometer says you went 9.2 miles. Take 9.2, divided by 10, and you get 0.92. Now, say your current speedo gear has 29 teeth. (Making that number up) Multiply 29 x 0.92, and you get 26.68. Your closest gear would be a 27-tooth gear, which will make your speedometer read a hair slow, but will be much closer than your current setup.

Make sense? The math is pretty easy.

-Joe

 

I found this really nice site in my travels through eBay!
Not only do they sell the gears for our trucks, but they have this great calculator to help you find the right gears for any setup.http://www.lowpricegears.com

The pricing seems to be pretty good with most gears sold and shipped for about $8.