Alright i got a 87 samurai. I have a spring over kit, with 30x10.50x15. At first i thought the tires look fine but now there looking a little small. I want to go up to a 31. I still have completely stock motor and gears. Im already missing 5th gear and can do at max 60mph. I wanted to regear the tcase to 4.9:1. will that slow it way down or will it bring it back to its original speed and get 5th gear back? i dont want to have to go any slower. thanks

That should bring your high range back close to stock with 30-31" tires.  And give you the better crawling as well. 

so faster high range and slower low range. kewl, thanks.