I doubt your front diff is the cause of the jumpy takeoff. The way a Ranger AWD works is that the rear wheels have to spin a portion of a turn before the front axles engage. Therefore if your rear wheels have traction when you take off and it's "jumpy" the greatest probability of that the clutch has issues. Polaris OEM clutches tend to provide jumpy take offs, even when new, it's the nature of the beast. Improvements can be made with clutch tuning kits by one of the various manufacturers. You might contact Hunterworks for advice. Another solution, on the expensive side but excellent for low speed driving, rock climbing or pulling loads is the Duraclutch. They always provide smooth engagement and do not wear belts when engaging due to their design. I suggest looking at their web site for a description. CVT clutches can stop working smoothly when they get dusty and dirty due to belt wear or have wear on internal part such as weights, buttons or broken springs. Belts can become glazed or hour glassed, particularly if driving at low speeds is done in high range. Any driving under 10 MPH should be in low range for best belt and clutch life.
Why is it that you think you need new front axles? There's no need to rebuild the front diff to change axles. They pull out without disassembling the front diff. I suggest downloading a digital Service Manual (about $10 on line) as well as an Owner's Manual (free on the Polaris web site) to become familiar with how the Ranger drive system works and how to repair it when necessary.
If you indeed do need new front axles choices are numerous. One thing to keep in mind is that although the OEM and aftermarket OEM replacement axles are weaker than heavier duty axles they act as a sort of "fuse" and break before the expensive internals of the transmission or front diffs break. There are many choices in axles available, ADR, SATV offers several and many others. Search the Internet for options.