Speedometer gear - Chevelle Tech
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post #1 of 11 (permalink) Old Dec 1st, 19, 9:34 PM Thread Starter
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Join Date: May 2002
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Speedometer gear

I swapped out the PG in my '66 ragtop for a Turbo 350. Speedometer is not reading correct now. What gear do I need to use at the trans. to get it corrected? And do I need to change out both gear that cable connects to and the one in trans.?

Thanks for your help
Todd
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post #2 of 11 (permalink) Old Dec 1st, 19, 10:01 PM
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Mark
 
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Re: Speedometer gear

You should be able to swap the gears(both) from the powerglide to the TH350. It may not require the drive gear(transmission gear) to be swapped, but you need to verify the tooth count and or color on both units to be sure.
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post #3 of 11 (permalink) Old Dec 1st, 19, 11:16 PM Thread Starter
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Re: Speedometer gear

I am using the original gear from the PG on the cable and whatever gear came with the trans. Do I need to match the gear on trans to gear on cable or vice versa?

Thanks
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post #4 of 11 (permalink) Old Dec 1st, 19, 11:41 PM
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David
 
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Re: Speedometer gear

The gear that drives the flexible speedometer cable from the transmission is what you need to change. Remove it from your PG and install it into the turbo 350 in place of whatever gear came with your turbo 350.

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post #5 of 11 (permalink) Old Dec 1st, 19, 11:53 PM Thread Starter
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Re: Speedometer gear

Will do. Thanks for your help
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post #6 of 11 (permalink) Old Dec 2nd, 19, 12:44 PM Thread Starter
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Re: Speedometer gear

OK so I did a little more research on this issue. I took the tail housing off the PG. It has a 7 tooth gear on shaft and a 20 tooth gear on speedometer "bullet" housing. I didn't use the original set up off PG like I thought. I used the gear set that came on the new turbo 350. I still need to see what that gear set is. The gear on PG shaft is metal and pressed on. Would not be an easy removal. So my question is now can I just change out gear on turbo 350 speedometer housing to XX gear to correct speedometer reading and what tooth gear is needed?

UPDATE: just pulled gear out of "bullet" housing on turbo 350....it has 18 teeth.
Which way do I go now????

Thanks as always for the help.

Last edited by todd j; Dec 2nd, 19 at 12:59 PM.
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post #7 of 11 (permalink) Old Dec 2nd, 19, 11:56 PM
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leo
 
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Re: Speedometer gear

use the 20 gear bullet, should just thread right in!!
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Leo Paugh
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progress has little to do with speed, but lots to do with direction

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post #8 of 11 (permalink) Old Dec 3rd, 19, 8:48 AM
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Dave
 
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Re: Speedometer gear

Quote:
Originally Posted by LeoP View Post
use the 20 gear bullet, should just thread right in!!
This ^^^!

Dave
USAF Retired (1968-1988)
UTC Aerospace Systems, Space Systems International - Retired (1989-2014)
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post #9 of 11 (permalink) Old Dec 3rd, 19, 11:22 AM
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Stan
 
Join Date: Jan 2004
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Re: Speedometer gear

I've posted my solution before. I always pursue the easy fix. Grab a handful of the color coded plastic gears. Download a speedometer app on your phone. Drive around and keep changing colors until you get as close as you need to be.
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post #10 of 11 (permalink) Old Today, 1:56 AM
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Thor
 
Join Date: Oct 2008
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Re: Speedometer gear

https://www.chevelles.com/shop/speedo.html
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post #11 of 11 (permalink) Old Today, 2:05 AM
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Eric
 
Join Date: Sep 2011
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Re: Speedometer gear

I've used the chart Thor listed on numerous cars. That chart has delivered accurate results confirmed by radar.
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