Th 400 speedo problem - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 3 (permalink) Old Jan 1st, 10, 05:09 PM Thread Starter
Join Date: Dec 2009
Posts: 1
Th 400 speedo problem

Speedometer will not calibrate correctly after 50 mph...
Will begin pegging forward after 50...
Replaced cable, checked for correct color/tooth gear (yellow)& checked 15 tooth drive gear (gray/silver)...
Do not know exact year of the th 400 in my 69 chevelle...

Currently running 15 255r tires & 342 gear

any advice or solution appreciated...
terryn69ss is offline  
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post #2 of 3 (permalink) Old Jan 1st, 10, 06:39 PM
Tech Team
Join Date: Dec 2007
Location: N CALIF
Posts: 50
Re: Th 400 speedo problem

Check out this site....

I came up with a 36 tooth gear (white) using

255 70 R 15 (28.9 diameter)
15 drive teeth
3.42 gear ratio
Smhigh is offline  
post #3 of 3 (permalink) Old Jan 1st, 10, 06:57 PM
Senior Tech
Join Date: Mar 2002
Location: Austin, TX, USA
Posts: 5,277
Re: Th 400 speedo problem

If it's pegging after 50 mph, but OK up to 50 mph, the problem is not the gears. There is a magnetically coupled disk arrangement connected to the pointer inside the speedo. Sounds like it's bent such that it begins to rub together above 50 mph.

68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
dnult is offline  
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