stangracr 10 Report post Posted September 14, 2011 Can someone tell me what speedo gear I need for 69 Mustang 351w with a FMX 3.50 gears in the rear. I changed from 3.00 to 3.50 and need to correct my speedo. ed Quote Share this post Link to post Share on other sites
Fordrevhead 29 Report post Posted September 14, 2011 Confirm u have 8 teeth on the drive gear then you need 22 on the driven but it isnt made. 21 is more common than 23 and it will also error on the high side instead of low which is better. Quote Share this post Link to post Share on other sites