Technical Turbo 350 speedo

Hi Guys, trying to get my speedo to work - turns out my turbo 350 doesn't have a drive gear.
anyone have any idea what color the drive gear should be in a 65 El Camino Turbo 350.
Seems there are all kinds of formulas and TCI has a really good calculator but need to know the tooth count on the drive gear - again, I dont have one !! Diff Ratio is 3.00 @ 1

Anyone able to offer any assistance ?

 

look at what drive gears are available, pick one, plug it into the calculator, see if the driven gear is available to work with that particular driving gear and your tire size/rear gear ratio.. If not, pick a different one, etc.

If you still can't figure it out, let us know. I'll give it a whirl.

 

Thanks Jim - Thats a great idea that was staring me in the face !

 

TH350 Speedometer driven Gears; 17, 18, 19, 20, 21 and 22 tooth.

 

$64 each? Are they really that much now?

 

Above posted gear is $12, output shaft gear (15-grey, 17-red, 18-blue or 19-yellow) is another $10.
http://www.laspeedometergear.com/700r4 speedometer gears th400 th.htm