Originally Posted by SquidsYJ
Joenate: You want your ratios in your front and rear differentials to match. Sometimes they are off by 0.01 and that is apparently OK. For example, 4.56 front and 4.66 rear is bad, but a 4.10 front and a 4.11 rear is acceptable.
This is correct.
The reason the exact mathematical ratio can differ is due to the tooth count of the gears in the differentials. You may find a slight difference (one or two HUNDREDTHS) in the actual ratio. For example. I technically have 4.55555555555~ gears in my front axle (41 tooth ring gear and 9 tooth pinion gear) and 4.5454545~ in my rear (50 tooth ring and 11 tooth pinion). These round to 4.56 and 4.55 respectively, and would be commonly referred to as 4.56s. You might hear them referred to as 4.55s. "4.10s" could actually be 4.09, 4.10 or 4.11. This small difference doesn't matter; mixing ratios like 3.07 and 4.10 will be an expensive disaster.