How to determine gear ratio on rear end out of vehicle?
 

Have a 1931 ccpu with a low gear ratio probably stock. My friend has three spare rear end assemblies. How would we determine the gear ratio of these units? What ratio would I want to use to get a little more top speed out of the stock motor?
Thanks in advance.
Charley

Re: How to determine gear ratio on rear end out of vehicle?
 

How about some pictures of what you got and maybe someone could help to put them together for you. Grant

Re: How to determine gear ratio on rear end out of vehicle?
 

Figure out a way to turn the driveshaft with one drum on one axle free to turn and the other one fixed (not turning).

Then follow procedure here, post #2:
https://www.fordbarn.com/forum/showthread.php?t=223904

Re: How to determine gear ratio on rear end out of vehicle?
 

To figure out the ratio with the unit apart, just count the teeth and divide the two. If its a 9/34 set then it'll be a std 3.78.