3.78 gears in 36 5 Window

[mfagan]

Have installed 3.78 gears behind a 39 trans in the 36 5 Window.

What turtle gears should be used for correct speedometer reading?

Thanks for any assistance.

 

[Tim Ayers]

19 tooth

 

[V8COOPMAN]

19 tooth

Yup....19! DD

 

[mfagan]

Where is a good place to look for one?

 

[19Fordy]

Here's a starting place. Contact seller and ask if he has your number.
https://www.ebay.com/itm/1937-38-39...ash=item5b425c67e6:g:RNMAAOSwBRFaTbB9&vxp=mtr
Also, check out Fordbarn Swap meet section of parts for sale.

 

[Tim Ayers]

Where is a good place to look for one?

I may have an extra. Let me check. I'll get back to you.

 

[blucar]

I have a #21 speedo drive gear in my collection of misc parts. Anyone have an idea what ratio it would be for?

 

[Charlie Stephens]

Look for one with a "wanted ad". I believe they are the same as late Model A, try Bratton's Ford Parts, (301) 829-9880. The "19" is correct but goes with the assumption you have stock 600-16 tires. There is a table on page 632 of the Green Bible.

Charlie Stephens

 

[40cpe]

I have a #21 speedo drive gear in my collection of misc parts. Anyone have an idea what ratio it would be for?

Probably for a 4.11. A 21 tooth turtle is about 10 percent slower than a 19 tooth, and the 4.11 is about 8.7 percent slower than a 3.78.

 

[Tinker]

Tire size makes a difference also. ***I didn't see charlie posted that.

Here is the chart however.

 

[blucar]

A big thanks to 40cpe/Tinker for the info.. I had it in the back of my head that the unit was most likely for a 4.11 ratio.. I recall taking it out of a '37 pickup I restored in the early '60's. Interesting that the chart lists a #21 as being for 4.11 w/650x16 tires.

 

[Seth Swoboda]

Where is a good place to look for one?

Michael Driskell at Thrid Gen Automotive in McMinnville TN. Lots of NOS parts.