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Old 11-04-2002, 09:58 PM
Jeff Murphy Jeff Murphy is offline
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Default Correct Speedometer Gears for Muncie in a COPO

My speedo is way off fast vs. actual (80mph indicated is more like 62mph) with only a modest 0.7" difference in tire diamater from stock (F70x15 vs. F70x14 original). The car was in storage for many years so the speedo didn't matter, but now that I'm driving it a bit, I'd like to have accurate readings. I'm guessing that it's either the speedo cable or that I've got the wrong speedo gearing in the tranny, or both.

Does anyone have experience with selecting the correct circle (drive) and pin (driven) speedometer gears for a Muncie 4 speed in a COPO Camaro with a 4.10 BE rear end or know what came factory? It seems like most cars should have an 8 tooth circle gear, but they come in two different diameters, 1.76" and 1.84", steel and nylon. There is also supposed to have been a 7 tooth 1.76", but some Muncie experts I've talked to have never seen one. All the repro catalogs list a 22t "green" gear as appropriate for 4.10s (which would indicate a 1.76" circle gear) but don't say how many teeth on it or specifically which circle gear it mates to.

I'm hoping to get a definitive or consensus answer on what the correct factory matchup was to allow reasonably correct readings with a 4.10 gear and stock 26.2" diameter tires. I am also hoping that I can get to the right answer without pulling the tail housing off the tranny to look at the circle gear and count teeth.

Do you think it might just be a bum speedo cable?
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  #2  
Old 11-05-2002, 12:59 AM
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Mr70 Mr70 is offline
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Default Re: Correct Speedometer Gears for Muncie in a COPO

Does your Trans.still retain the proper gear adapter?It should be right where the Speedometer cable screws into it.If it is missing,this could be the reason.Anything with a 4:10 or higher rearend,Chevrolet used this gear reducing adapter on.GM still sells this part over the parts counter,albeit in a different design then the original,for Auto,and Manual trans.
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Old 11-05-2002, 04:04 AM
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Default Re: Correct Speedometer Gears for Muncie in a COPO

GarnetM20, The Chevy parts book calls for a small dia. 8 tooth drive gear and a 24 tooth yellow driven gear, without an adaptor, when using a small output tailhousing. From experience I know it works. Hope this helps -- Crash
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Old 11-05-2002, 07:47 PM
Jeff Murphy Jeff Murphy is offline
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Default Re: Correct Speedometer Gears for Muncie in a COPO

Thanks. That's what I'm going with.
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Old 11-05-2002, 08:17 PM
Keith Tedford Keith Tedford is offline
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Default Re: Correct Speedometer Gears for Muncie in a COPO

Our Chevelle with the M20 has the adapter between the cable and the transmission.
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