Take it easy on me since I am a new Samurai owner(6 months). LOL!   I was given a complete 4.57 thrid member and I have stock 86 sami with SPOA and 29" tires.  I lightly trail ride here in Florida in mostly sand.    I have found a 4.62 tracker front diff for $150 I would like to install.  I am on a tight budget and cannot afford to spend the $$$ on having a 4.57 diff built right now.  Will this combo hurt anything.  I know Ford and Chevy did different ratios like 4.09/4.10 and 3.50/3.55 from the factory so I was thinking 4.625-4.571=.054 difference was not that bad. I have read a difference of 1-2% in gear ratio is not that bad for a 4x4 but what about a Samurai??    What do you think???

They do that so the front will pull the Back for better steering, you can make up the difference by letting some more air out of your back tires if it bothers you.

I agree with the front pulling the back like ford's 4.10 rear and 4.09 front but they also did a 3.50 rear and 3.55 front.   So that has me curious about that combo.

I don't see a problem on low traction surfaces

I agree with ecoast. Even on trucks with evenly paired diffs we have all run our vehicles (at some time) in a slightly off-matched condition simply by running half worn tires on one end and mounting new rubber on the other.  You can easily have a half of an inch of difference or more in tire diameter simply because of wear.  The manufacturer/s do plan for and allow a percentage of difference for play within the drive trains.  How much?  I've heard up to 3%.  I think the drive trains are rarely perfectly matched for a variety of conditions (such as above).  

you will find that by having lower gears in the front you will be pushing it instead of the front pulling the rear witch helps you steer but nothing should happen on slick surfaces but make it harder to control .