Since I didn't see a better place I guess I'll throw this in here.
So I am getting an NV4500 for my truck this week. I plan to completely tear it down despite that fact it's in good working order and refresh all the syncros put in some upgrades and cryo EVERYTHING. My next order on the list is a rear end upgrade. I love my 3.07's but I really want a locker or LSD in the rear, and rear discs. I've been talking to some 2nd gen guys and they keep saying skip the D80 and go straight to an AAM 11.5 from a later 3rd gen or 4th gen. I know the 3rds come in 3.73:1 (which is a lot higher then I wanted), but the 4th gens do have a 3.42:1 rear option.
Now I haven't done much research on widths, bolt patterns, etc. I'm just wondering if anyone in here has done one of these. I'd love to find a 3.08 or similar bigger rear end with an LSD or Locker option, but I haven't seen much for a Dually rear with that. I use my truck heavily for towing so I want a strong rear end. I'm ok with having to ditch the factory springs if needed (likely will anyways) for a 4 link or similar. I'll also likely have a air suspension with load compensation.
currently I am 3.07 no OD so 60 mph is ~1950 still get decent economy, but would really love to reduce it.
with 3.07 and Nv4500 overal is 2.2411:1 in 5th making 60mph with 235/80-17s is ~1400
3.42 with Nv4500 is 2.4966:1 overall making 60mph ~1600 right about where I want to be
3.73 with Nv4500 is 2.7229:1 overall making 60 mph ~1750
4.10 with Nv4500 is 2.993:1 overall making 60 mph ~1900
I tow mostly highway and I plan to have upgraded turbos and fueling to have power at 1500-2800 peak My biggest concerns are egt's towing.