The problem is the way are main drive gear is part of the input shaft. In a Dana 18 case the main drive gear fits on the splines of the transmission output shaft. For a lower gear set, Tera low 3.15 ratio, we would need a different input shaft. When installing a lower gear set, the gear on the input shaft is a different size, less teeth if i remember right. We need someone to make a shaft with the appropriate gear. Other than that the internals appear to be the same as a Dana 18. This shaft is the same reason we cannot install the Saturn over drive. I don't have the resources to take this one on. However Advanced Adaptors, who still makes the Saturn overdrive does, might be able to help us out. If we could install the overdrive at 25% reduction we could install 4.88, 5.13 etc, gears for a better crawl ratio but still be good on the road.
In a dana 44 axle the break point is 3.73 and down, 3.92 and up. the difference is about 1/4" on the carrier, closer to pinion gear for 3.92 and up. What Mahindra did was to add about 1/8" to the carrier. So for example when i installed my front RCV axles i bought the 3.73, 30 spline carrier and added the ring gear spacer to get back to what Mahindra did and it works fine with the stock gears. This is what the OX locker does as well.