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Discussion Starter · #1 ·
perhaps you could gimme a hand. On my '79 with NP203 TC, I was wandering what driven gear I need. I have a 100mph ground speed indicator, 3.23 gears and 31x10.50 rubber. Is this a Dodge dealer item, or could I get one just anywhere?
 

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You can get them from the dealer, or pull one out of a J/Y. I want to say that you need the green one??? Not sure. There were a couple of different ones used for the different rear end ratios and tire sizes and such and they were color coded. The dealer does have them tho and I don't think that they are too expensive.
 

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Discussion Starter · #3 ·
Well, it appears I need to know how many teeth the gear needs. Again, 100mph speedo, 203TC, 3.23 gears. Any ideas?
 

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You will need to take your gear out, and count the teeth. Chryco makes lots of different gears. As a rule of thumb, if you need your speedo to read faster, you need LESS teeth on the replacement gear. As a general rough rule, each tooth is about 3 mph at 60 miles per hour. So if your speedo is reading 6mph below actual, get a gear with 2 less teeth. Let us know what you need. I have quite a few of extra gears at the house.
 

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MudFlap said:
Well, it appears I need to know how many teeth the gear needs. Again, 100mph speedo, 203TC, 3.23 gears. Any ideas?
I have not forgotten about you. Send me your email address and I will send you 3 scanned pages from the parts book. I'm little slow...old age is taking it's courese!{bigeyes}
 

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Discussion Starter · #6 ·
[email protected] will work I checked my odometer with the mile markers on the highway and it appears I am about 25% slow. For 100 miles travelled, I showed 80, and for 125 miles, I showed 100.

Next question is this - If I put in an aftermarket electric speedometer, are they easy to re-calibrate according to tire size, gear ratios, etc?
 
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