Speedo gear question
Thread Starter
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Post Fiend
Joined: Oct 2003
Posts: 9,176
Likes: 4
From: Western Central NV
Speedo gear question
Our second truck is an 88 Dodge D250 2wd, 4sp. This weekend I removed the 4:10 gears in the rear end and installed a 3:54 gears. Now I need to change the speedo gear in the tranny. I clocked it today I'm about 15% slow. I read 8.5 tenths to one mile. Does anyone know the formula to figure the right number of teeth on the gear in the tranny?
Thanks. I went to the Dodge dealer today and they weren't much help. I guess I'm spoiled our local Ford Dealership has parts people that know what is going on. Anytime I need something for my 86 F250 4x4 the Ford dealer knows where to look. He can read books, not just a computer screen like the Dodge dealer.
Thanks. I went to the Dodge dealer today and they weren't much help. I guess I'm spoiled our local Ford Dealership has parts people that know what is going on. Anytime I need something for my 86 F250 4x4 the Ford dealer knows where to look. He can read books, not just a computer screen like the Dodge dealer.
Elder User
Joined: Sep 2006
Posts: 798
Likes: 1
From: Alma Arkansas
http://www.go.jeep-xj.info/HowtoSpeedoGears.htm
The above link is meant for Jeeps but the same may apply to your dodge.
The above link is meant for Jeeps but the same may apply to your dodge.
New User
Joined: Jan 2008
Posts: 0
Likes: 24
FTE calculators 
https://www.ford-trucks.com/calculators/index.php
Located in the "Articles" drop down box
or
http://www.tciauto.com/Products/Tech...eedo_gears.asp
https://www.ford-trucks.com/calculators/index.php
Located in the "Articles" drop down box
or
http://www.tciauto.com/Products/Tech...eedo_gears.asp
Thread Starter
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Post Fiend
Joined: Oct 2003
Posts: 9,176
Likes: 4
From: Western Central NV
Originally Posted by Krochus
http://www.go.jeep-xj.info/HowtoSpeedoGears.htm
The above link is meant for Jeeps but the same may apply to your dodge.
The above link is meant for Jeeps but the same may apply to your dodge.
That is exactly what I needed. That will give me a place to start.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
Start with this: Count the number of teeth on the speedo cable gear. Say for instance it's 22 teeth. Take 85% of that number, or 22 x .85 = 18.7 teeth, then round that number up to 19 teeth and you are as close as you can get.
All you need is the percentage.
All you need is the percentage.
