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post #1 of 4 Old 02-16-2012, 09:09 PM Thread Starter
jduress
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Speedometer questions?

Is there anyway to calibrate your speedometer? It is a 1985 cj7 with the t5 tranny. I realize it gets its signal from a cable but mine is off by 5mph. The reason is probably the oversized tires that were on it when I bought it. Just wondering if there is a way to adjust the speedo somehow thanks!


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post #2 of 4 Old 02-16-2012, 09:14 PM
VACJ7
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The only way to compensate for the bigger tires is to change the speedo gear.

If you have a GPS it is pretty easy to calculate. You only need three things: Tooth count of gear that is currently installed, Speedometer reading, and GPS reading. Run it up to 45 or so and record speedometer reading and GPS reading. I do it at a couple different speeds.

X= speedometer reading / GPS reading
New gear = X * current tooth count

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post #3 of 4 Old 02-16-2012, 10:59 PM
only in a jeep cj
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The speedometer is a set calibration from the factory and requires much know how to adjust it, but that is not the correct solution in your case. As said, the speedo gear in the transfercase is the solution. It is under where your cable screws in to the rear section. 1985 with a T5, you most likely have a 31 tooth gear and will need one a few teeth less so it spins a tad faster and bumps up the speedo.

http://www.transmissioncenter.org/sp...e_and_jeep.htm

Ed
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post #4 of 4 Old 02-17-2012, 07:18 AM
lucdog
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Quote:
Originally Posted by only in a jeep cj
The speedometer is a set calibration from the factory and requires much know how to adjust it, but that is not the correct solution in your case. As said, the speedo gear in the transfercase is the solution. It is under where your cable screws in to the rear section. 1985 with a T5, you most likely have a 31 tooth gear and will need one a few teeth less so it spins a tad faster and bumps up the speedo.

http://www.transmissioncenter.org/sp...e_and_jeep.htm
I believe this same place sells a adapter that has different ratios. While more expensive ($65) they do work, its installed on the TC externally, the cable then screws into it. They do work well, I have 2. One of them has 40,xxx miles on it.

They are avaible in different ratios.

Bill

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