speedometer calibration
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Cargo Master
Joined: Oct 2003
Posts: 2,833
Likes: 4
From: Jefferson, Iowa
speedometer calibration
I purcahsed my 78 F-100, about a month ago, and i had someone follow me and flash their lights when i hit 55. My speedometer said 42 when i was going 55. I have a 18 tooth speedometer gear. What size should my new gear be?
Posting Guru
Joined: Dec 1999
Posts: 1,903
Likes: 2
From: Copley, OH
To make the speedo read higher, you need the cable to be spinning faster. That requires a smaller driven gear.
If their speedo was right, and it may not be, you'd need a gear:
18T x (42/55) = 13.75
That would be a 14T gear which AFAIK doesn't exist, The smallest available is 16.
If their speedo was right, and it may not be, you'd need a gear:
18T x (42/55) = 13.75
That would be a 14T gear which AFAIK doesn't exist, The smallest available is 16.
Posting Guru
Joined: Dec 1999
Posts: 1,903
Likes: 2
From: Copley, OH
Pull the tailshaft housing, remove the old gear, slide on a new, replace the seal while you're at it and reassemble. There's probably a snap ring or something, I've never been inside a T-18 but they are reputed to be very simple to work on.
