Gear ratio figuring help

[jim in seattle]

So I jack up just one side, put it on a stand. Mark drive shaft and tire, and turn the wheel while counting revolutions of both wheel and shaft. I did this several times and got the following results:

8 wheel = 11 shaft
5 wheel = 7 shaft

This figures to 1.375 and 1.4 respectively.

WTF? What am I doing wrong?

 

[abodyjoe]

turn the wheel once and count how many times the shaft went around.

 

[67Dart273]

On an "open" rear, when turning just one wheel, you want TWO wheel turns and no of shaft revs

So divide 8 / 4 to get two, therefore also divide 11 shaft /4 = 2.75 rear gear

Or another way, divide your 11/8 = 1.375, then x2 = 2.75 rear gear

Or divide your 7/5 =1.4, then multiply x2 = 2.8

This is because "going through" the spider gears causes a x2 factor

 

[jim in seattle]

Oh okay. Thanks.

So I guess that means I have 2.76?

1969 Barracuda 318 / 904

 

[fishy68]

Oh okay. Thanks.

So I guess that means I have 2.76?

1969 Barracuda 318 / 904

Yes