AAM 11.5 information

[Croatan_Kid]

I've been curious about this axle since I bought it from a fellow member (Don't remember who, but he lives in Apex) and I've slowly, but surely, been uncovering more information. Some of the things were easy to find.

It has a lot in common with the previous AAM 10.5. They use the same hubs, hub bearings, spindles, and brakes as far as I can tell. It only uses one carrier and gears are made to their proper thickness to work...sort of like HP 60 carriers. They use a threaded carrier bearing preload adjusters, just like a 14 bolt as well. The axle tubes neck down to 3.5" at the spring perch area though. That probably had something to do with using the same lower spring plates as 1/2 ton axles or something. I flipped mine and used regular u-bolts with the plates on top.

There are a few differences though, but nothing terrible. The 11.5 obviously uses an 11.5" ring gear...which is HUGE. The 11.5 also doesn't have the 3rd pinion support bearing on the end of the pinion snout like a 10.5 does, nor does it have a removable pinion setup. Instead of a standard yoke, you can get a Dodge style 4 bolt flange or the GM yoke/damper. The yoke/damper will be a 1410 or 1480 depending on application. I haven't quite figure out if they used 1415 and 1485 series joints in the GM drive shafts, but it's very possible since AAM liked to use them. They're an odd size and completely backwards in thinking...you would assume a 1415 would be bigger than a 1410, when in fact, they're almost the same with the exception being the end cap to end cap dimension is smaller on a 1415. Same with the 1480 vs. 1485.

1410 - 1.188" diameter caps, 4.188" width

1415 - 1.188" diameter caps, 4.178" width

1480 - 1.375" diameter caps, 4.188" width

1485 - 1.475" diameter caps, 4.178" width


So, you can see that if you were to use a 1410 in place of a 1415, it would be a hair too wide and either would not fit in the yoke or the cir-clips would be bowed out and probably fail. Otherwise, it would fit in the driveshaft end because of the same diameter caps.


Now, here's what I've really been trying to uncover....yokes! I've currently got a 63", 3.5" diameter 1410 shaft in the rear of my Silverado. I'm not very keen on the HUGE damper that's on the pinion yoke and I'd like to swap it to a regular, u-bolt style, pinion yoke. I didn't think I could do this without buying one of the yokes made for competition sled pullers. They're usually billet and quite expensive!

However, with some digging around at http://northerndrivetrain.com/ and a trip out to my shop to verify a few things, I made a discovery! The 10.5 and 11.5 pinions splines share the same diameter, spline count, and spline pressure angle. In other words, I can use a regular old, extremely common, 14 bolt yoke on my 11.5! There's a catch though; the newer axles...1998 and newer, I believe (when they changed to AAM) use a larger pinion seal ID. The older seal was a 2.200", but the new ones are 2.370". They made up the difference using what I would describe as a "pinion saver". Basically a sleeve that presses over the ground seal surface of the yoke.

Here's what I'm talking about: http://www.northerndrivetrain.com/product/AAM-26060977.html

It makes sense to me. If your seal wears a groove in that...you can replace it for 8 bucks instead of buying a whole new yoke.


Now I know I can use this yoke: http://www.northerndrivetrain.com/product/NDT-3-4-8001X.html and get rid of the big old damper and shed some weight in my driveline. It will also save me from having any problems in the future when the damper decides to go bad like a harmonic balancer on an engine. Not only that, but I can now use a yoke with u-bolts instead of straps. It may seem like something that I'm over thinking, but my OCD kicked in and I like everything to be the same.

I figured I would share my findings in case anyone else wanted to use an AAM 11.5 in their rig or if you have a 2500HD that needs a new pinion yoke.


Also, as a disclaimer, I'm not associated with the guys at Northern Drivetrain, but I have bought from them before and I like their website because they list a lot of technical information and that's very handy in doing research. You could probably buy any of this stuff from your favorite local vendor.

 

[Bobbytjr]

Good article and thank you for the info and I wonder if you could help me? I am switching from a 10 and a half inch ring gear on my 2013 HD gas to 11 and a half inch ring gear from a Duramax and I might have to cut the rear shaft a couple inches and reweld and balance and also the bearing cups are a different size on the differential yolk"bigger" than on the drive shaft yoke. Do you know if they have a universal u-joint for that purpose? Thanks

 

[Croatan_Kid]

Honestly, what I'd do is go ahead and bolt the 11.5 under the truck and get everything else buttoned up. Then, pull a measurement to see how much shorter the driveshaft needs to be. You'll measure from the face of the output shaft on the transfer case (assuming it's 4wd) to the face of the yoke on the axle. When you go to the driveshaft shop, they're going to cut the axle end of the driveshaft when they shorten it, so just have them replace the whole driveshaft yoke with a 1410 setup. In the future it will make replacing the u joint at the pinion easier to find and likely cheaper than a 1350 to 1410 conversion joint.

Does the truck have a steel driveshaft or an aluminum one?

 

[OnlyOneDR]

Now you can go get a 2014+ Power Wagon locker as the 11.5 is the same.

 

[Croatan_Kid]

If you can find one. I looked at them a while back and they are scarce, so when you do find them, they're 1500+.

 

[Bobbytjr]

Honestly, what I'd do is go ahead and bolt the 11.5 under the truck and get everything else buttoned up. Then, pull a measurement to see how much shorter the driveshaft needs to be. You'll measure from the face of the output shaft on the transfer case (assuming it's 4wd) to the face of the yoke on the axle. When you go to the driveshaft shop, they're going to cut the axle end of the driveshaft when they shorten it, so just have them replace the whole driveshaft yoke with a 1410 setup. In the future it will make replacing the u joint at the pinion easier to find and likely cheaper than a 1350 to 1410 conversion joint.

Does the truck have a steel driveshaft or an aluminum one?

It is a crew cab w/8ft bed 4wd and has two steel driveshafts with a center support bearing. The place I called in town here wanted both shafts so when they cut and weld the back shaft they can balance both shafts which I do not see necessary; maybe I'm wrong. Thank you for your help!

 

[geardaddy]

the aam 11.5 is a very strong rearend. if you are putting a posi in it, get one from the 2003 up dodge, it is much better than the gm tried and trashed gov-lok... yes they do need the complete d-shaft to balance it.. if the center slip does not have a mother spline on it, be sure to mark it so it goes back together the same..

 

[Croatan_Kid]

The 11.5 govlocks are about the only ones that are worth a damn. Lots of high horsepower guys still use them, but they'll all explode if they get worn out too much.

My preference would be a Detroit TrueTrac. It has a 3:1 bias vs the Dodge AAM version at 2:1. Basically, it's tighter. Pricey though. Every aftermarket traction device for an 11.5 is going to kill 1000 bucks.