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.

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?

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..

Re: No speedo reading after TH350 swap
 

An interesting idea, how would i be able to spin that fast enough by hand? I've heard of hooking up a drill to the back of the speedo but it's real tight up there.

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



:chevy::chevy::chevy:

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.

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