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Discussion Starter #1
Hiyo:

I'm finally fixing my speedo, which hasn't been right since I changed rear gears a year and a half ago.

From Fred's great web page (http://www.geocities.com/~69_chevelle/speedo.htm), and from the speedo gear chart here (http://www.chevelles.com/shop/speedo.html), I know I need a 22 tooth speedo driven gear (PN 3987922 silver) and an 8 tooth trans gear which isn't listed on Fred's page. Does anyone here have the part number for that one? The GM parts guy can't do anything for me without the number.

Also, the 22 tooth gear has a second part number 3860345 green; how can I tell which one to get, or does it matter?

Thanks!!!

Oh yeah, this is for a TH350.

[This message has been edited by Dave66 (edited 05-25-99).]
 

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Measure the output shaft diameter were the spedo gear mounts. If the diameter is 1.180 with a 5/16 width clip then the part # is 6261784. If the diameter is 1.190 and is a 1/2 inch wide clip then it is # 8640055. If it is a splined shaft the # is 6261794. If it is not any of those sizes then there may not be one availible for your trans in that tooth count. You may want to try an independent shop.

[This message has been edited by Mike Sadoian (edited 05-25-99).]
 

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Dave & Mike
Looked through my parts manual again and:
- 6261784 looks to me like it should be 6261794 - Mike, check me out here.
- The way I see it, 3987922 silver driven gear should be used with an 8 tooth drive gear.

Mike, If you can provide additional info on drive gears, I'd be glad to add to my page. Frankly, I tried to dig out the information but wasn't able to make any sense of all the part numbers for 3sp, 4sp, PG, THM350, THM400.

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Fred Aldrich
Web Site: www.GeoCities.com/~69_chevelle



[This message has been edited by Fred Aldrich (edited 05-25-99).]
 

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Discussion Starter #4
Mike and Fred:
Thanks for the help! I still have the trans gear that came with the trans (its a TCI) and I can measure that, and hopefully get the gears for this weekend. Thanks again!
 

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Dave,
The speedo gears 3987917 thru 3987922 (17-22teeth) are the smaller diameter gears, about 13/16. These are designed to be used with larger diameter speedo drive gears with 7, 8 or 9 teeth. Some books call the 3987922 gear silver and some call it gray. It's definitely gray.
The 3860345 thru 3860348 gears (22-25teeth) are a tiny bit larger in diameter, about 7/8in, and are designed to be used with a smaller drive gear. I personally have used big with little and vice versa with no problem. Just a few weeks ago I said that these gears are about $2-$3 each. Well it has been a while since I have bought one. Now they are about $6. But all the numbers I gave above are still available from Chev. I try to keep at least one of each.

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Yes, if it will reach.

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