AAM 11.5

[v8coupe]

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.

[RCCUMMINS89]

I've owned just about every gear ratio.......3.73 were IMO by far the best over all. Unless I was doing over 70 my mpg were phenomenal. That 70 mark is where they started to drop.

For heavy weight we can use the gearing. A ve just doesn't have the transmission and engine set up like the new trucks do.... therefore again, gearing helps. 4.10s are a little over kill though for stock tires.

[v8coupe]

I've owned just about every gear ratio.......3.73 were IMO by far the best over all. Unless I was doing over 70 my mpg were phenomenal. That 70 mark is where they started to drop.

For heavy weight we can use the gearing. A ve just doesn't have the transmission and engine set up like the new trucks do.... therefore again, gearing helps. 4.10s are a little over kill though for stock tires.

I'll be 12v VE with NV4500 from an 01, regular cab, regular box dually. It's about as light as you can get in a 1ton. I will most likely be pulling the cab to do the 5-speed swap (currently a 727 non OD) and boxing the frame and rewiring it since most of it is a mess. I do drive the truck a few times every month for parts runs, metal runs, etc. So I'd like good all around mileage. I also tow at 65-70 regularly as most of the highways are that or higher around here. Having just completed a east coast to MN tow I can say the 3.07/nonOD setup isn't a fan at all, but the engine ran great at 65 even in the hills.

[v8coupe]

Will a tuned engine with a proper low rpm towing twin do ok with a 3.42 rear?

[flyin6]

I built an AAM 11.5

In my 2011 Duramax. It is as strong as they get. I added a Grizzly locker and 4.56 gears to mine. Again, this is a Chebby with the D-Max engine making over 1100 ft. lbs. and it likes some RPM. I also run larger tires.

Setting up the axle is similar to the 14 bolt, from which it is derived. The axles are huge in both the Chevy and the Dodge applications, but if you are sourcing the Chevy axle stay with a 2010 or earlier as the 2011 had a strange 180mm bolt circle, much larger than the 6.5" we are all familiar with. They did that because the gross weights of these newer trucks is approaching semi territory and a larger bolt circle is required for the increased loads and the larger bearings. Speaking of which, in 2011, the bearing size of the actual diff increased in the GM axles. I believe the Dodge axle still uses the smaller bearings which, BTW are overkill already.

The Grizzly locker is the most streetable locker I have ever used...It's just great, although you will give up some rear tire life because of it, but you won't give up one ounce of traction!

[Philip]

If you going to limit yourself to using a 5 spd. Go with a deeper rear gear. Use 3:54 or deeper. The gear spacing on eather 5 spd used by Dodge are pretty bad. A 3:42 isn't much over the 3:07's. The holes in the 5spd gearing will show just as bad with eather one of those gears. 3:54's and up you can live with the holes to some extent.

Myself If I was going to the AAM axle. I would stay with the 3:73's. They aren't a bad tow gear. If you have a break down on the road. Finding a replacement 3:42 axle might be tough.

A LSD in your current axle is easy. Just find a Dana 70 LSD carrier that is 4:10 and down. Order a LSD rebuild kit for it with 35 spline side gears. Install the new kit. Throw it in the axle.

[u2slow]

My biggest concerns are egt's towing.

Interesting... taller ratios equate to more load and higher EGTs. You may want to get a diff that has 3.54 or 3.73 already to try out. You can also gear a Dana 80 to 3.31. At least with a 5speed, you have full control of your driving style, and your EGTs to a large degree.

I put a Dana 80 in my W250. The SRW drum version is ~5" wider; the SRW disc is ~6" wider. There's no shortage of trashed 2ndgens out there for parts. If you want a good posi, last year for the Powr-lok is 98.

The Lockright for the 70 and 80 is the same part number (35 spline, that is), so you could get one now, and re-use it in a D80.