12" AAM rear diff 'anti spin' - Dodge Cummins Diesel Forum
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post #1 of 89 (permalink) Old 05-08-2019, 10:45 PM Thread Starter
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12" AAM rear diff 'anti spin'

1st post. Thanks for having me on board. Just drove my truck off the lot today. So far I'm very impressed. I had better love it... Anyways. As I figure out what these parts are actually, the first question I had had/have is identifying the exact manufacturer and technology used in the rear end. I know it's a 12" AAM, similar to the 11.5" used in previous models including GM 3500. I loved the G80 in my last 2 GM 3500 11.5 AAM. But I don't think my truck uses the G80. I believe it uses a Torsen clutchless LSD. Some folks dont like it as much as the G80 locker but others prefer it. Regardless, if anybody has any info on exactly what in the pig back there, please chime in.


My 1st Ram: 2019 Laramie 3500
6.7 HO Aisin AS69RC. Borg Wagner 44-48 4x4. 12" AAM Rear end. CCLB. Single Rear Wheel. Max Steel. 295/70/18 (35x12) Mickey Thompson MTZ P3. No lift/no level.
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post #2 of 89 (permalink) Old 05-09-2019, 01:55 PM
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It is a torsen style LSD. Has a 2:1 torque bias ratio. No friction modifier is required and works better if none added (some have had noise issues requiring friction modifier).

Btw: It's actually a 12.5"

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2006 Ram 3500 4x4 6sp, F&R TrueTrac, EFI Live, GT3782R, Dual Disc
2018 Ram 3500DRW 4x4, Stock for now
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post #3 of 89 (permalink) Old 05-09-2019, 08:26 PM
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I believe you meant 11.5 and last I knew the bias on a 3500 is set higher for a slightly more aggressive diff.
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post #4 of 89 (permalink) Old 05-09-2019, 11:52 PM Thread Starter
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Quote:
Originally Posted by lpennock View Post
It is a torsen style LSD. Has a 2:1 torque bias ratio. No friction modifier is required and works better if none added (some have had noise issues requiring friction modifier).

Btw: It's actually a 12.5"

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The window Sticker said 12" but I'll happily take 12.5. How do you feel this adds up to the auto locker in the GM 11.5 version? I like that differential on my 2 most recent truck.
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post #5 of 89 (permalink) Old 05-09-2019, 11:54 PM Thread Starter
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[QUOTE=Jhenderson;28977281]I believe you meant 11.5 and last I knew the bias on a 3500 is set higher for a slightly more aggressive diff.[/QUOTEIt was the 11.5 until they udgraded the 6.7 to HO version. Now it's at least the 12" or apparently maybe the 12.5?

My 1st Ram: 2019 Laramie 3500
6.7 HO Aisin AS69RC. Borg Wagner 44-48 4x4. 12" AAM Rear end. CCLB. Single Rear Wheel. Max Steel. 295/70/18 (35x12) Mickey Thompson MTZ P3. No lift/no level.
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post #6 of 89 (permalink) Old 05-10-2019, 12:54 AM
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Quote:
Originally Posted by Jhenderson View Post
I believe you meant 11.5 and last I knew the bias on a 3500 is set higher for a slightly more aggressive diff.
Now that I think about it. It is a 11.5 that was upsides to a 12. I hadn't heard of them changing the bias. Last I checked it was 2:1.

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2018 Ram 3500DRW 4x4, Stock for now
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post #7 of 89 (permalink) Old 05-10-2019, 12:58 AM
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Originally Posted by esminbritt View Post
The window Sticker said 12" but I'll happily take 12.5. How do you feel this adds up to the auto locker in the GM 11.5 version? I like that differential on my 2 most recent truck.
In high difference in traction between sides I think the GM diff is better. For normal driving the torsen style is better.

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post #8 of 89 (permalink) Old 05-10-2019, 06:36 AM
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Originally Posted by lpennock View Post
Now that I think about it. It is a 11.5 that was upsides to a 12. I hadn't heard of them changing the bias. Last I checked it was 2:1.

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The new 12" in the '19's are clutch type now. They also have 4.250" axle tubes, larger hubs and a different wheel bolt pattern.

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post #9 of 89 (permalink) Old 05-10-2019, 07:43 AM
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In a srw? Why doesn’t AAM list a 12 in diff?
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post #10 of 89 (permalink) Old 05-10-2019, 08:06 AM Thread Starter
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Originally Posted by Jhenderson View Post
In a srw? Why doesn’t AAM list a 12 in diff?
I think they upgraded to the 12" to handle the HO version of the 6.7.

My 1st Ram: 2019 Laramie 3500
6.7 HO Aisin AS69RC. Borg Wagner 44-48 4x4. 12" AAM Rear end. CCLB. Single Rear Wheel. Max Steel. 295/70/18 (35x12) Mickey Thompson MTZ P3. No lift/no level.
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post #11 of 89 (permalink) Old 05-10-2019, 08:06 AM
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In a srw? Why doesn’t AAM list a 12 in diff?
I am not sure which trucks get the update. Some info says the high out put trucks and some says the max tow.

copy from this link:

New front and rear axles on the 2019 Ram 2500 and 3500 Heavy Duty have been engineered to improve durability, handle industry-leading payload and towing capabilities, and minimize NVH, as well as take advantage of opportunities to optimize weight.
The Ram 3500 Heavy Duty with the Max Tow Package uses an all-new, larger 12-inch AAM rear axle with 4.25-inch axle tubes, larger head, tail and differential bearings, and new O-ring style axle shaft hub seals. The limited-slip differential uses a friction plate design, while the serrated axle pinion and driveshaft flanges are upgraded to handle the increased torque.
The 9.25-inch AAM front axle on the Ram 2500 and 3500 Heavy Duty 4x4 include improved pinion seals and revisions to the housing to mitigate noise, vibration and harshness. The connector for the front-axle disconnect has been improved to enhance durability and the disconnect shield is upgraded for better protection from road hazards.

Link: https://www.turbodieselregister.com/...-night.265813/

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post #12 of 89 (permalink) Old 05-10-2019, 08:08 AM Thread Starter
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The new 12" in the '19's are clutch type now. They also have 4.250" axle tubes, larger hubs and a different wheel bolt pattern.
That's what I'm trying to verify. Seems odd they would go back to clutches after running helical gears on the recent 3500's. Any idea why? Is it a torsen style clutch system?

My 1st Ram: 2019 Laramie 3500
6.7 HO Aisin AS69RC. Borg Wagner 44-48 4x4. 12" AAM Rear end. CCLB. Single Rear Wheel. Max Steel. 295/70/18 (35x12) Mickey Thompson MTZ P3. No lift/no level.
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