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post #1 of (permalink) Old 02-12-2001, 12:47 AM
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Speedo Calibration

I plan on installing 33" tires on my 2000 TJ it has a stock auto tranny and a Dana 35 Rear. I am assuming that the speedo will be off due to the increased tire diameter, if so do they make an after market transmission speedo gear to compansate for the larger tires?

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post #2 of (permalink) Old 02-12-2001, 01:21 AM
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Re: Speedo Calibration

Yah that's not a problem. I forget the numbers but you do an equation that determines the percentage of the tire increase, then you pull the speedo gear from the transfer case (one bolt), and count how many teeth are on it. Then you work out how many teeth on the gear make up the percentage amount you got from the tires. ei 30 teeth on gear. 10 percent tire difference, so 10% of the 30 teeth makes 3 teeth. Now you add the 3 teeth onto the 30 you have and voala! You need a new gear with 33 teeth so that the speedo gear turns 10% slower to make up for the tires.
Now just add you numbers into this instead. Cost me $14 for a new gear in my old truck.

'88 Sahara, 4.2, auto.
post #3 of (permalink) Old 02-12-2001, 01:22 PM
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Re: Speedo Calibration

Hey, once ou do the math, and find a source, please let me know. I have 33's waiting in the garage, waiting for the lift kit (tax return!) and will be faced with the same problem.

Likewise, if mine go on first, and I solve it, will post here...


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post #4 of (permalink) Old 02-12-2001, 02:12 PM
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Re: Speedo Calibration

Terry Howe used to have a gear applet on the web. Does anyone know if that exists in a new location? All you had to do was put in your ratios and it would tell you the number of teeth (based on your t-case). It was super simple. Also, to change the gear takes all of about 5-10 minutes and is cheap. The jeep dealers carry them or will order them.

258 4.0 Head/MPI,NV4500,D300,4.10's,HS9500
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post #5 of (permalink) Old 02-12-2001, 02:39 PM
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Re: Speedo Calibration

http://www.ring-pinion.com/Tech Libr...edometers.html

Winter Harbor, Maine
'81 CJ-8 Scrambled!
It's a Jeep, Chevy, IHC kinda thing!
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post #6 of (permalink) Old 02-12-2001, 08:26 PM
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Re: Speedo Calibration

Here is a link to Terry Howes new site. He is the main guy here, and he is definately the drivetrain god!

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post #7 of (permalink) Old 02-13-2001, 12:07 AM
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Re: Speedo Calibration

I went to a tranmission shop and they let me look in a box full of the gears all sizes. They let me take three and bring back the ones that did'nt work. But l live in fly over country. IN,KY

79 CJ5 258 firecracker red
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