My 2014 4/4 has a 1:39.1 final drive fitted. From memory 70mph = 3000 rpm in 5th.
It’s Sigma powered with a Mazda box and the change is also mentioned as an entry in the owners manual.
Thanks again for your post, Kevin. I looked at the RPM in the OBD and at the speed today. 70 mph is 112.65 km/h. I drive at 3000 rpm just 119 km/h. That corresponds pretty much to the difference in the differential ratio 1: 3.9 vs. 1: 3.71.
Have you ever driven a 4/4 with 1:3.71 to describe the difference?
Was your axle a prototype, a one-off? Or does your dealer know if this axle can be bought? Even 1:3.9 would be an improvement if I could get one.