1945-46 ford 1/2 ton pickup rear differential,how to figure the ratio ?

biglee · #1 (**permalink**) 02-09-2004, 10:23 PM

Hi all,
I just put a 1945 ford 1/2 ton pickup rear differential,open banjo,on ebay.
But I don't know how to figure out the gear ratio.
Can anybody help me out here. I'm getting swamped with ratio questions.
Is there a standard ratio that they put in the 1945-6 ford pickups back then ?

Thanks,
Lee

old farmer · #2 (**permalink**) 02-10-2004, 03:53 AM

biglee, try this. With the axle off the ground, mark the input shaft and the wheel that turns when the input is turned. Turn the input and count how many turns it takes to get one turn of the wheel. Or you could take the cover off and count the number of teeth on the gears.

46fordtruck · #3 (**permalink**) 02-10-2004, 11:05 AM

Farmer is right about the turning thing, but don't disasemble the rear to get the ratio, since that would require removing the axle tubes, since these rears don't have covers. They did have a standard ratio, usually a 3.78, other ratios were optional.

biglee · #4 (**permalink**) 02-10-2004, 03:23 PM

Hi all,
thanks for the help.
I turned the input shaft 2 complete revalutions to 1 revalution of the drum+2".
What ratio is this ?
Thanks,
Lee

old farmer · #5 (**permalink**) 02-15-2004, 08:24 AM

Biglee: Forgot to mention that I think you have to multiply by 2. So you would be 4/1. Likely a 4.11/1 ratio. Sounds like a truck type ratio!