The Ford Barn

Afordman31 · 07-17-2021, 08:06 PM

Jacked up the drivers side rear wheel, put a piece of tape at the 6 o'clock position. Put a mark at the 12 o'clock position on the drive shaft splined end.
I then turned the rear wheel forward one full revolution and the driveshaft moved not quite 1 7/8 turns clockwise. What ration rear end do I have? Your help is much appreciated!

Patrick L. · 07-17-2021, 08:13 PM

I would think it should be a 3.78.

jayvee34 · 07-18-2021, 06:40 AM

Math wise: 2X1.875=3.75 Most likely a 3.78

alexiskai · 07-18-2021, 06:57 AM

I believe you’re supposed to rotate the rear wheel twice and then note the drive shaft revolutions. Multiplying your current result by 2 gives 3.7, which I guess is a possible result if you have an early ‘28, but otherwise you should keep going to get a more precise answer.

nkaminar · 07-18-2021, 07:09 AM

If you want to be really precise, count the driveshaft revolutions with 20 rotations of the wheel and then divide by 10.

Patrick L. · 07-18-2021, 08:57 AM

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I think the ratio available at the time were 3.70 [early], 3.78 [later] and 4.11 [truck]. I think by far most had 3.78.

But the difference between 3.7 and 3.78 won't be noticeable.

Afordman31 · 07-20-2021, 10:11 PM

Thank all of you for your replies. Appreciated!

07-17-2021, 08:13 PM	#2
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Model A Rear End Ratio I would think it should be a 3.78.

07-18-2021, 06:40 AM	#3
jayvee34 Senior Member Join Date: Apr 2021 Location: St. Augustine, Fl. Posts: 437	Re: Model A Rear End Ratio Math wise: 2X1.875=3.75 Most likely a 3.78 __________________ IN GOD WE TRUST - SEMPER FIDELIS John Last edited by jayvee34; 07-18-2021 at 06:48 AM.

07-18-2021, 06:57 AM	#4
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 2,350	Re: Model A Rear End Ratio I believe you’re supposed to rotate the rear wheel twice and then note the drive shaft revolutions. Multiplying your current result by 2 gives 3.7, which I guess is a possible result if you have an early ‘28, but otherwise you should keep going to get a more precise answer.

07-18-2021, 07:09 AM	#5
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,899	Re: Model A Rear End Ratio If you want to be really precise, count the driveshaft revolutions with 20 rotations of the wheel and then divide by 10. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

07-18-2021, 08:57 AM	#6
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Model A Rear End Ratio Sponsored Links (Register now to hide all advertisements) I think the ratio available at the time were 3.70 [early], 3.78 [later] and 4.11 [truck]. I think by far most had 3.78. But the difference between 3.7 and 3.78 won't be noticeable.

07-20-2021, 10:11 PM	#7
Afordman31 Senior Member Join Date: May 2010 Location: Michigan Posts: 580	Re: Model A Rear End Ratio Thank all of you for your replies. Appreciated!