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Discussion Starter #1
ive been looking everywhere for the correct driven gear to correct my speedometer.i have a th350. my drive gear is 19 tooth, the diameter of my tires is 26", and i have a 2.73 gears. ive gone to a calculator and gear chart and it says i need a 40 tooth driven gear, but i cant find one. where am i going wrong?
 

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Discussion Starter #3
ive searched that site and many like it. they dont even come close to having a 40 tooth driven gear for the th350. there drive gears are nowhere close to mine as well.
 

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Could you use a external gearbox like I did with 2004r? Unscrew cable at tranny, screw in small gearbox w/proper gear, screw in cable to box. Done. Used it on my 2.56 to 3.42 conversion.
Auto Electric in Norfolk VA did mine for less than $100. 757-627-5187
 

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im not sure i havnt researched that, but im on a tight budget, so for that price ill contenue to use my app on my phone. im really close as it is by being one tooth off. but the closest i found was on ebay and theres went from 39 (which i have) to the next size being 44
 

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Deputy Director Region 6
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I changed both my drive & driven gears to get mine done for $30.
I sent them a email with my info & they told me what gears to get !
I sent it to [email protected] !!
 

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Discussion Starter #8
i was hoping not to have to change my drive gear. it would be much simpler if i could do just the driven gear. if i had known, i would have snag`d the gear from the car that i got the rear end from. steve: i will prob have to pay the extra to get both and tough it out. ughhhhh lol.
 

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I should have my old speedo gears & I will check to see what drive gear I had & maybe you can find a driven gear for that if you can't find the 40 tooth you need ?
 

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i have some speedo gears and the gm speedo gear chart i will look up yours later tonight when im done in the shop.i just put 273 s in my 86 and dont think it was a 40 tooth driven gear
 

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i was running 273 s and a 25.5 in tire and the speedo gears i have are 17 tooth red drive gear and 38 tooth green or light blue. the speedo and odometer were dead on. going a 40 would make your speedo about 5 slow. what actual tire size are you running
 

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Discussion Starter #12
i have 17" rims and i cant remember what the rubber is. but i took the tape measure out and got the dia of the tire. it came out to be 26" all of the calculators i use for that tell me i need a 40 tooth for the 19 tooth drive gear that i have.
 

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i found the gear combination you want to run but it is for a 25.1 in tire not a 26 in.give me your actual tire size and i will look it up for you if not i will look today to see if i have the gear and adapter you need
 

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I solved my problem by buying a cheap GPS unit;;they are pretty accurate,and you wont be pulling your hair out trying to calibrate what you have.
Most all indicate your current speed...usually reads about 2 mph faster than what your actually traveling.
 

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Discussion Starter #16
ya i have a speedometer app on my phone that uses gps, but id like to have the one in my car work properlly so i can use my phone as a phone. this is almost not worth my time to be honest. i figured i was over looking something. the guy at the GM dealership looked it up as well and they dont make that one anymore. but he did give me some numbers to a couple of companys that say the have them. i just have to call them tomorrow. i waited to late today to call.
 

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TrannyMike
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I solved my problem by buying a cheap GPS unit;;they are pretty accurate,and you wont be pulling your hair out trying to calibrate what you have.
Most all indicate your current speed...usually reads about 2 mph faster than what your actually traveling.


kstmbowtie, look and see if there is a Transtar Industries near you. It doesn't even have to be real close because they ship all the time. They are about the biggest trans supplier in the country. Maybe they have it. If that doesn't work PM me and I'll see if my local distributor has one. They'll even ship to you from here if I do it for you. You'd have to pay a little more but not much since it's a small part. :beer:
 
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