Who knows speedo bullets?

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Jan 22, 2006 | 08:43 PM

Greg

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Just another Corvette guy

Joined: Feb 1999

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From: Palm Springs, CA.

Who knows speedo bullets?

Hi Gang,
I'm looking for a good tranny guy who knows his speedo gears.
I have my trans out right now and I'd like to correct this. The previous owner of my '70 corrected his bouncing speedo by replacing the driven gear in the speedo bullet. However, he didn't install the correct one so the speedo reads too fast all the time. The driven gear has 18 teeth and is sort of a whiteish/gray color. I'm running 3:55 gears in the rear. Do you happen to know the correct gear for this application?
Thanks,
Greg

Jan 22, 2006 | 08:49 PM

markdtn

Le Mans Master

Joined: Aug 2003

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From: Chattanooga TN

Need to go to your friendly neighborhood GM dealer. Tell him what tires are rear gear you have and he can recommend and sell you the right driven gear.

Jan 23, 2006 | 01:36 AM

Star79

Melting Slicks

Joined: Apr 2004

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From: Montreal Qc.

Here's good link with gear colors and some formulas to calculate which one you need. Then you can go down to the dealer and get what you need.

http://www.transmissioncenter.net/sp...n_______va.htm

Jan 23, 2006 | 03:08 PM

454Can-Am

Racer

Joined: Jun 2001

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From what I always understood ----- each tooth make a difference of 2 1/2 miles per hour.................. smaller spins faster and larger spins slower. Hope this helps ! Rick

Jan 23, 2006 | 08:34 PM

Greg

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Just another Corvette guy

Joined: Feb 1999

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From: Palm Springs, CA.

Thanks for the replies guys.
Great link Steve, lots of good info but they seemed to cover mostly automatics. Mine is a four speed and I couldn't find my application.

Jan 24, 2006 | 07:59 AM

markdtn

Le Mans Master

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From: Chattanooga TN

Quote:

Originally Posted by 454Can-Am

From what I always understood ----- each tooth make a difference of 2 1/2 miles per hour.................. smaller spins faster and larger spins slower. Hope this helps ! Rick

That may be generally true, but it depends on if it is a 4 speed which has a small gear or a TH400 which has a much larger driven gear. Each tooth is a ratio of the total teeth. For example, if you have 30 teeth, 1 tooth is a 3% difference; if you have 20 teeth, 1 tooth is a 5% difference roughly.

Jan 24, 2006 | 08:13 AM

comp

Team Owner

Joined: Sep 2003

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From: eville in

Quote:

Originally Posted by Star79

Here's good link with gear colors and some formulas to calculate which one you need. Then you can go down to the dealer and get what you need.

http://www.transmissioncenter.net/sp...n_______va.htm

Jan 24, 2006 | 08:54 AM

ruby76

Drifting

Joined: Sep 2004

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From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark

Hey greg, didn't realize you had your own thread regarding driven/drive gears before I posted mine. thanks for posting on mine as well.

I agree too, that the websites I keep finding don't really have the 4 speeds covered to well. The one above DOES mention the t-10 4 speed though. the pics of the driven gears next to it shows my delimna. The green 22 tooth has a larger diameter gear cross section than the white/natural 19 tooth that I need. So my driven gear does not contact my drive gear. My existing driven gear (22 tooth green) is 1 7/8" in diameter at the gear teeth, the new replacement 19 tooth is 1 3/4" in diameter and won't contact the drive gear