Speedometer Adjustment
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New User
Joined: Jun 2004
Posts: 18
Likes: 0
Speedometer Adjustment
My in dash speedometer is reading about 10mph slow at 40 mph actual. If I'm going 40, it read sabout 30. The truck does not have the original tires on it. That is probably this problem. Question is: is there any way to calibrate or adjust this?
Cargo Master
Joined: Feb 2004
Posts: 2,081
Likes: 175
From: Central Texas
That's too far off to be just tires. I would suspect that the rear end gear ratio has changed at some point. A ratio change will make your speedo be off by the same ratio. If your speedo reads 15 when you are going 20 and, if you dare, reads 60 at 80, then that's most likely a gear change. The easiest way to correct this would be to change the speedo gear at the tranny according to the rear end ratio.
Postmaster
Joined: Dec 1999
Posts: 2,813
Likes: 6
From: Connecticut
Your local Ford dealer can get the gear you need. If it's only 10 MPH, then you need to get a gear with one less tooth than what's on the end of the cable now. Pull the end of the cable out of the tranny and take the gear off the cable. Take the gear to the parts dept and tell them you want a gear identical to this one, but one less tooth. That will make the speedo read closer, if not correct now. I have the parts books to look them up if you want me to. Send a private message and I'll help you out.Don't let the dealer say they're obsolete, because they're not. I do this all the time.
Barry
Barry
