You have to understand that there can be several correct ratios for the same size tire depending on the engine size, transmission type, and how it's going to be driven. And a guy with a big block Chevy powered vehicle is going to require different ratio than a guy with a 4.0 engine will. So just because some guy says x.xx ratio is ideal for 33's or 35's doesn't mean jack because you have no idea what vehicle/engine/transmission type he's thinking of.
Yes 4.56 would be ideal for 33's and so would 4.88 for 35's with the 4.0 engine and 5-speed manual transmission. But not for your 42RLE transmission that has an extra-steep Overdrive ratio that drops the highway cruising rpms way down, well below what the 5-speed manual transmission does. The 42RLE's Overdrive ratio is .69 which means its cruising rpms drop by 31% when the Overdrive kicks in. The AX-15 5-speed has a .79 Overdrive ratio so it doesn't drop the engine nearly as much. Not to mention it takes a bit more power to run an automatic than it does a manual transmission.
For 33's, you really do want nothing else than 4.88 but 5.13 would be better with your 42RLE automatic. Both of those ratios produce ideal engine rpms on the highway, they will NOT be too high. In fact they'll be right on where you want them and you'll notice they're entirely appropriate. I run 5.38 gears for my 35's and 42RLE automatic. I actually wish my highway rpms were a bit higher. The 5.38 is FAR better than the 4.88 I used to run but slightly more highway rpms would be nice.
So come away with the understanding that one ratio that is good for 33's with one engine and transmission type is not going to be appropriate for a different engine and transmission type. Stop listening to the kid at the 4Wheel Parts sales counter. Odds are he's driving Chevy or Ford pickup with a big V8 and his idea of a good ratio wouldn't be correct for our Jeeps.
