I think it depends where you are starting from, with 3.73's you will want to re-gear after 35" tires. With the 4.27/4.46 you can probably get away with it for a while (35's are not an issue). Just watched a video with a manual 2.3 Badlands wheeling a level 8 trail in Utah using the stock 4.70:1 gears on 40's without a problem with having enough power or torque.IMO, going up an inch or two you can feel it but no need to re-gear.
Anything more than that I would re-gear.
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