Driven Gear
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Posting Guru
Joined: Jul 2009
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From: Ventura, CA
Driven Gear
Ok so i pulled my driven gear so I could figure out what gear I need to correct how the speedo reads. Right now it seems to be off 1 mph for every 10 so when it reads 60 im actually doing 66 according to my phone gps. So heres what I found. its a 20T gear and looks like this:
I have no clue how to find what gear i need so any help is appreciated. Thanks guys!
I have no clue how to find what gear i need so any help is appreciated. Thanks guys!
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 787
From: Simi Valley, CA
Ok so i pulled my driven gear so I could figure out what gear I need to correct how the speedo reads. Right now it seems to be off 1 mph for every 10 so when it reads 60 im actually doing 66 according to my phone gps. So heres what I found. its a 20T gear and looks like this:
I have no clue how to find what gear i need so any help is appreciated. Thanks guys!
I have no clue how to find what gear i need so any help is appreciated. Thanks guys!
Adding a tooth will slow the speedo down 5-7 MPH: C4OZ-17271-A .. Red Nylon Speedometer DRIVEN Gear-21 teeth, type 3A = ////
16 thru 21 tooth nylon DRIVEN gears have been used since 1960, all are available from Ford/autoparts stores.
Take this gear to the parts store to match it up. Some teeth run this-away: //// some teeth run that-away: \\\\
Make sure when you do the comparo that the shaft is pointing up, as it is now. Otherwise you'll be comparing bassackwards.
If you install a \\\\ DRIVEN gear, the DRIVE gear on the output shaft will chew it up in a NY minute.
Elder User
Joined: Apr 2008
Posts: 619
Likes: 1
From: Montpelier, VA
One more tooth on the driven gear should do it. Here is a reference program that calculates it for you. You just fill in drive gear, rear end ratio, and tire diameter (which you can easily look up). We should make a sticky note for the program.
Speedometer Calibration Program - Method 1
Speedometer Calibration Program - Method 1
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 787
From: Simi Valley, CA
One more tooth on the driven gear should do it. Here is a reference program that calculates it for you. You just fill in drive gear, rear end ratio, and tire diameter (which you can easily look up). We should make a sticky note for the program.
Speedometer Calibration Program - Method 1
Speedometer Calibration Program - Method 1
What else does he need to know?
Posting Guru
Joined: Nov 2008
Posts: 1,255
Likes: 2
From: Santa Monica, CA
Dave, I have a thumbnail that looks kinda like yours and a finger that looks worse!!
Who needs tattoos when we have our own slick battle scars?
now, back to your speedo gears.....
Elder User
Joined: Apr 2008
Posts: 619
Likes: 1
From: Montpelier, VA
Bill, I agree with you. I simply posted that program for reference. Someone else may do a search on "driven gear" and it may help them.
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Posting Guru
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Hahaha I've got a big ol scar on my forearm and a few others on various fingers that put that thumb to shame!!! It's all part of the fun, each ones got a story lol
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