Speedometer

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Mar 30, 2006 | 05:56 PM

Roy in TX

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Joined: Mar 2005

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Speedometer

I changed the center section in my diff. Took out a 3:70 and installed a 3:25. With the 4 spd I have this really made my highway cruising much better (along with improved gas mileage), howerver my speedometer is off considerably. I estime about 8 miles an hour. Was instructed earlieer on this forum to change the speedo gear in the transmission. Took it out today and found out that its a 20 tooth. The gear comes from LMC from 19 to 22 tooth. My question is , which way do I go ??? Anyone got suggestions ? Thanks. Roy.

Mar 30, 2006 | 07:03 PM

barry

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Joined: Dec 1999

Posts: 2,813

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From: Connecticut

You don't say which way it's off, too high or low. If it's too fast, add 0ne tooth, too slow, use a gear with one less. There's a formula to figure it, but I can't remember it.

Barry

Mar 30, 2006 | 07:43 PM

Bdox

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Joined: Sep 2005

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From: Lake Tahoe, Nevada

The speedo will read 52.7mph at 60 mph now, assuming that it was right on originally. That's 87.8 percent of 60 mph. Since the speedo cable is the driven gear, it needs to have fewer teeth to speed it up. So: 20 teeth times 87.8 % is 17.56 teeth to be accurate. So since you have to choose a whole number of teeth, buy an 18 tooth speedo gear. You will be very close.