Most guys that want to re-gear...want to go the other way (lower), to compensate for larger tires. Unless you have a diesel (CaseyS), I can't imagine wanting to go higher on the gearing...especially with the 5-cyl. It can barely pull 35"s on the highway with the stock 4.56 gearing, and if you run 37"s it probably means 3rd gear at 60 mph. On any other vehicle the solution is to re-gear to 4.88s or 5.13s but, on the H3 that's not possible without a torch, four-weeks of shop time, and $6000. The lowest ratio you can install in the front AAM-7.625 is 4.56s....so you're stuck with em.
Alpha guys can drop from 4.10s to 4.56s to help overcome some power loss (Kflips) from larger tires. But 5-cly guys are just plain out of luck.
The least expensive route to lockers is to find a wreck AP equipped truck and swap the entire front & rear assemblies. This is a 3-hour job, and you can expect to pay $1000 each used, locked, axles. You must find an 09-10 with a 3.7L to get the cast-iron, locked front axle. That's a tall order...not many around, wrecked or otherwise.
The next cheapest route is to install new lockers into your existing axles. Depending on the manufacturer...lockers will cost you around $750-$1100 per axle PLUS labor. There are basically three choices for selectables...OX, Eaton, or ARB. Labor should run around $300 per axle. You will need to install relays, wiring, & switches (for electric)....or on-board air compressor (for air)....or a cable (for mechanical) engagement.
Yes, you can swap the internals from your aluminum to a cast iron case, if you like.
No, you cannot run different gearing in the front & rear.
Yes, you should re-flash your PCM to adjust shift points and speedo calibration (even for tire size changes). It makes a difference.
