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06-23-2020, 06:02 PM
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#1 |
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Registered User
Join Date: Dec 2013
Location: CT
Posts: 109
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No speedo reading after TH350 swap
I recently ordered a transmission from Summit Racing and after installation I'm getting no reading on the speedo. I picked up a new cable from GMCPaul and no change. I swapped out the bullet and plastic gear and still nothing. The speedo was making this very low "scraping" noise before swapping out the tranny but it was working fine. I'm stumped here. The old plastic gear and bullet looked OK.
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06-23-2020, 06:24 PM
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#2 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,704
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Re: No speedo reading after TH350 swap
If you pull the bullet and gear out can you make the speedo work by rotating the gear
By hand? |
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06-23-2020, 06:40 PM
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#3 |
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Registered User
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,804
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Re: No speedo reading after TH350 swap
Could be the speedometer drive gear is wrong or gone.. Remove the bullet and driven gear.. Peek through the hole in the transmission output housing.. If present, the drive gear can be seen on the output shaft..
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06-23-2020, 08:26 PM
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#4 | |
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Registered User
Join Date: Dec 2013
Location: CT
Posts: 109
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Re: No speedo reading after TH350 swap
Quote:
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06-23-2020, 08:30 PM
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#5 |
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Moderator
 
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,204
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Re: No speedo reading after TH350 swap
Remove the cable end from the bullet and place the chuck of a battery operated drill on the cable end.
Start out slow...and try both directions...some speedo's dont register in reverse... If the speedo works the issue would be the drive gear on the shaft not meshing with the driven gear in the bullet. There are a multitude of gears, both drive and driven.... As an example see https://www.ebay.com/i/132711079839?...SABEgJN__D_BwE 
__________________
Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox 
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06-23-2020, 09:07 PM
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#6 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,704
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Re: No speedo reading after TH350 swap
A quick twist will tell you.
If you feel tension and the needle moves then it’s working. You don’t need to maintain any mph. |
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06-24-2020, 12:20 AM
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#7 |
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Registered User
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,804
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Re: No speedo reading after TH350 swap
Do you have the drive gear from the old transmission?? Do you know the tooth count on the drive gear that was in the old transmission?? If the answer is "no" to both questions, go to this site, use the formulas there to compute the gears you'll need.. Otherwise, you'll spend a LOT of time guessing and switching gears around..
https://www.tciauto.com/speedometer-gear-calculator |
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