Ram 1500 Gearing Options
I just bought a 2015 Ram 1500 4x4 EcoDiesel. As much as I want to do the deletes and lift the truck, I want to tackle the plagued front axle first. There are no traction devices for these trucks due to the fact that the design has weak points, allowing them to grenade. Short of a custom-built 9-inch IFS or a 2500 AAM 9 1/4-inch solid axle swap, what other truck companies with stout IFS axles could be considered to swap into my truck? Or would going custom IFS or SAS be the best route?
Your truck is equipped with a 215mm ZF differential that is slightly larger than the 205mm that was in the 2011 and older models. Though the differential appeared under Ram 1500s starting in 2012, sometimes it takes a while for aftermarket gear and traction device manufacturers to develop products for a new axle. Developing a gear ratio isn't as simple as adding teeth to the ring gear and taking them away from the pinion; it takes a lot of R&D, testing, and refining for each and every ratio. The same thing goes for traction devices like limited slips and lockers.
We spoke to Just Differentials (justdifferentials.com), which unfortunately had very little information about the availability or even an ETA of either aftermarket ratios or traction devices for the 215mm ZF axle. It appears that you are limited to only available factory ratios at this time, which stop at 3.92.
Further complicating things are various reports from the field that ZF welded the ring gear to the carrier rather than using conventional ring gear bolts. Though the information we found on the subject was vague and even somewhat contradictory, it appears that possibly only 2013 models have welded differentials, so you may be in the clear. But if not, a welded ring gear means a gear swap is going to mean swapping carriers as well. There are also reports that swapping in a differential from an earlier (2011) Ram is a bolt-in, but that only nets you the ability to install up to 4.56 gears without any available traction devices. The earlier differential uses a smaller (205mm) ring-and-pinion, and you'd still have relatively weak CV axleshafts. Plus, the costs of sourcing an earlier differential and then doing a gear swap are probably prohibitive.
If you're dead set on lower gears and a front limited-slip or locker, your only options are going to require extensive custom fabrication in the form of a custom IFS system and a solid-axle swap. Neither option would be something we would recommend an average home fabricator attempt. At the end of the day you'll need to evaluate just how badly you want to upgrade your Ram and your budget, then make a decision accordingly. Or you could sit back and wait for a couple of years in the hopes that the aftermarket eventually addresses the ZF front axle.