which speedo gear...

39portlander

39portlander

Well-known member
For my 39 P/U I did not use my original TT and got a later one with the center bearing. Now today I installed my speedometer cable and realized I had two drive gears.

The one on the left is marked 9-34 and below 19, the right hand one in 9-37 and below a 21. I realize the 19 and the 21 are the tooth count on these drives, the question is were I have changed gears from 4:11 to 3:54's which one would work best or do I need a different one altogether.

Any input would be great. Scott
 

Attachments

  • 001.jpg
    001.jpg
    79.4 KB · Views: 51
What tire size do you plan to use on the rear? If you use 600x16, the #18/11-39 turtle would be correct as 35fordtn said. If you are planning to use larger tires on the rear your speedometer may be off a bit with the 18 and require a different number turtle to correct the speedometer reading, possibly a 17.
 
Thanks for the input, as I read the Chassis parts book I did notice tire sizes were noted for the diff numbered gears.

I have 6.00 x 16 Coker classics 3" WW on all four corners, now to the Fordbarn "swap meet" to find an 18 :D. Scott
 
A 17 just sold on ebay a couple of weeks back for $250! How rare are those? Does someone have a list of all the turtles that were made for reference?
 
bobgrice said:
A 17 just sold on ebay a couple of weeks back for $250! How rare are those? Does someone have a list of all the turtles that were made for reference?
Click to expand...
Get a copy of the 28-48 Ford parts book (Green Book) and you will see two pages of the information you need.
 
Here is a chart for which speedo gear to use. The chart uses factors of the rear gear set and tire size. Hope this helps too.

163175
 

Attachments

  • SPEEDO CHART.jpg
    SPEEDO CHART.jpg
    190.9 KB · Views: 352
Again thanks for even more input on this matter. I'm glad I have this problem with matching proper speedo gears, with the reply's were all smarter because of it.

Want to also thank Mr. Model A Ed Williams with the little tidbits over the phone this morning. scott
 
So it looks like I have a 4.11 on my '33 Sedan. Speedo gear is marked 9-37 21. With the rear axle raised, I rotated the drive shaft 2 revolutions to turn the wheel 1 revolution. (One wheel remains stationary) So am I correct in thinking the gear set is 4.11?
 
Think that is correct, but I always check it with both wheels turning together to eliminate the differential issues. I like to check them with the car on the ground and push if forward one tire revolution and count the drive shift revolutions. This gives you a very close guess.
 
The 17 is for sale at Brattons along with the housing which is also needed. It is for Model A so the shaft inside the gear needs to be changed to the square hole style for the cable.
 
So in 1933, or other years, what determined the axle ratio for each model? My sedan has 4.11 gears, so did all sedans come that way?
 
You must log in or register to reply here.
Back
Top