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Speedometer gear (teeth) for 4:56 ring/pinion?

 
Old 08-16-2007, 12:13 AM
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1ARACE
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Default Speedometer gear (teeth) for 4:56 ring/pinion?

I have a 24 tooth speedometer gear in now and it is way off, and I have checked the Helms shop manual, Haynes manual, GM dealership, and a few parts stores, and no one can tell me the tooth count for 4:56.

So does anyone know off-hand? Or is there a conversion chart available?

Thanks

With original size, F70 x 15, tires

Last edited by 1ARACE; 08-16-2007 at 12:19 AM. Reason: Tire size
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Old 08-16-2007, 12:17 AM
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i've looked into this some. As far as i can tell you can't get a gear for a 4.56

you would have to change the drive gear to even come close. And that requires taking the tranny apart.

You need a converter box.

I multiply all readings by 0.6 ie 100mph = 60mph.
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Old 08-16-2007, 12:24 AM
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We have charts pasted on our web site at this link that will help you. It looks like you need a 20 tooth gear! You can adjust the gear by using a simple rule that one tooth equals five miles per hour. In most GM driven gears, the last two numbers are the tooth count required for the car. If you have a 24 tooth gear and the stock drive gear, then you will be way off on the speedo.

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http://willcoxcorvette.com/advanced_...&keywords=gear

Or,


Last edited by Willcox Corvette; 08-16-2007 at 12:29 AM.
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Old 08-16-2007, 01:04 AM
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I had a 20 tooth in originally, which was off a lot more than than the 24.

At the GM dealership they listed a 39 tooth, next highest from 24...would that work?
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Old 08-16-2007, 01:19 AM
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No, you need to pull the transmission and see what the drive gear tooth count is. I suspect this is the problem since the 20 tooth is not working properly. While the dealer may list a 39 tooth gear, I've never seen such a beast and for sure it will not mesh with the teeth on the drive gear inside the transmission.

In MOST (and not applied to the sheet I posted) case's the last two number indicate the tooth count on the gear. The gears that will work with the stock drive gear for the factory transmission are 3987918, 3987919, 3987920, 3987921, and 3987922. Any other gear will not mesh with the teeth on the drive gear inside the transmission properly. Each of the above mentioned driven gears are identified by both color and tooth count!

In the chart that was posted, some of the gears have number changed to the gears above.

What transmission do you have? And if you can see inside the hole, what color is the drive gear? If you can see the gear, try to count the teeth (Impossible, but you can try).

Is the speedo reading fast or slow and by how much?

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Old 08-16-2007, 01:28 AM
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M21, close-ratio. Yellow (24 tooth) now, was a green (I believe, will check tomorrow) 20 tooth.

Pacing traffic, I would "guesstimate" around 20-25mph above what it should be.
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Old 08-22-2007, 01:58 AM
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You may have a calibration problem in the speedometer too!
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Old 08-22-2007, 08:27 PM
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You need to put the 20 tooth driven gear back in and use a 3932220 ratio adaptor... Crash
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Old 08-22-2007, 08:59 PM
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3932220 adapter is no longer available. However if you are not running the reduction adapter this is your problem. You can solve this by using this part.

http://willcoxcorvette.com/product_i...ducts_id=24539

Thank you,

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Old 08-22-2007, 09:18 PM
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The 3932220 adaptor is in stock at Crash Enterprises...
[email protected]
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Old 04-15-2018, 08:04 PM
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Default 4.56 gears

Originally Posted by DrainSurgeon77 View Post
The 3932220 adaptor is in stock at Crash Enterprises...
[email protected]
If you have a 4.56 rear gear then your Muncie will need the 6 tooth(if my memory serves me) steel drive gear which mates with a STEEL driven gear. I know this because I own a 65 365hp AC coupe with factory 4.56 gears. It has a STEEL driven gear not plastic. I assume all Muncies are the same.
Just noticed that this is a very old post.

Last edited by Billygold; 04-15-2018 at 08:06 PM.
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