Speedometer Gear Size 1972 th350

[88gtstreetrod]

I need to replace the bullet and speedometer gear in a TH350 transmission. I can not seem to find what the stock size is (color)? or the size I need for the tire size I am running. Any help is appreciated.

I have seen the calculators and can't use them because i don't know the transmission drive gear ratio.. if you know what a stock transmission gear drive ratio is for a 1972 TH350 is.. that would be great

Truck has the 3.07 rear end and tires are 28 inched tall

Thanks!

[kaycee]

So you have no speedo gears at all ??? Look in the hole you took the speedo bullet out of and see what color it is then you can find what you need. I went to the salvage yard and took 1 out of a Caprice then I looked up what the drive gear I needed and I ended up having 1.Go by a trans. shop they might hook you up on the gears.

[tdangle]

You don’t need to figure the trans ratio as it is 1:1 in 3rd. Jut plug in your final drive ratio and tire size and the # of teeth for the driven speedo gear. You can look in the speedo gear hole and see the color. Look up the tooth count and use that number. I believe tciauto.com has all the info you need on their speedo Calc page

[88gtstreetrod]

Thanks!

[County]

I just replaced mine in a '69 c10 with th350. I used the "natural" color, 19 tooth.

[88gtstreetrod]

Originally Posted by County

I just replaced mine in a '69 c10 with th350. I used the "natural" color, 19 tooth.

Perfect, thank you

[randy.powell]

So a "heads up" to all that may be looking for this info - DO NOT use the gear calculator on the BTO website! No matter what variables you plug into their formula the answer comes out the same. I've discussed with them and they know the formula is in error but for whatever reason they can't fix/disable/or remove from their website. That being said, they are more than happy to talk to you on the phone and tell you what you need.
B/R,
Randy