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-   -   12" AAM rear diff 'anti spin' (https://www.cumminsforum.com/forum/4th-gen-powertrain/2500351-12-aam-rear-diff-anti-spin.html)

esminbritt 05-08-2019 10:45 PM

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.

lpennock 05-09-2019 01:55 PM

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"

Sent from my SM-T350 using Tapatalk

Jhenderson 05-09-2019 08:26 PM

I believe you meant 11.5 and last I knew the bias on a 3500 is set higher for a slightly more aggressive diff.

esminbritt 05-09-2019 11:52 PM

Quote:

Originally Posted by lpennock (Post 28976909)
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"

Sent from my SM-T350 using Tapatalk

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.

esminbritt 05-09-2019 11:54 PM

[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?

lpennock 05-10-2019 12:54 AM

Quote:

Originally Posted by Jhenderson (Post 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.

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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lpennock 05-10-2019 12:58 AM

Quote:

Originally Posted by esminbritt (Post 28977435)
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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NIsaacs 05-10-2019 06:36 AM

Quote:

Originally Posted by lpennock (Post 28977483)
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.

Sent from my SM-T350 using Tapatalk

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.

Jhenderson 05-10-2019 07:43 AM

In a srw? Why doesnít AAM list a 12 in diff?

esminbritt 05-10-2019 08:06 AM

Quote:

Originally Posted by Jhenderson (Post 28977569)
In a srw? Why doesnít AAM list a 12 in diff?

I think they upgraded to the 12" to handle the HO version of the 6.7.

NIsaacs 05-10-2019 08:06 AM

Quote:

Originally Posted by Jhenderson (Post 28977569)
In a srw? Why doesnít 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/

esminbritt 05-10-2019 08:08 AM

Quote:

Originally Posted by NIsaacs (Post 28977553)
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?

Satan's Chariot 05-10-2019 10:17 AM

Quote:

Originally Posted by NIsaacs (Post 28977553)
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.

I'm not seeing a different wheel bolt pattern. I'm not saying you're wrong, but I didn't see it. That would be stupid to have a two bolt pattern options.

NIsaacs 05-10-2019 10:54 AM

Quote:

Originally Posted by Satan's Chariot (Post 28977701)
I'm not seeing a different wheel bolt pattern. I'm not saying you're wrong, but I didn't see it. That would be stupid to have a two bolt pattern options.

I think it is just the dually.

The Max Tow package returns and brings with it larger rear rotors, a 12-inch ring gear, bigger bearings and shafts, the latter requiring a larger bolt circle, so whether or not you get Max Tow every dually will have a different bolt pattern than SRW trucks. With Cummins power, only the MegaCab 4x4 2500 has a tow rating of less than eight tons.

https://www.turbodieselregister.com/...ram-hd.265793/

esminbritt 05-10-2019 01:35 PM

My single rear wheel came with the 12Ē pig according to the sticker. I also measured the discs when they were putting on my MT MTZ. The rear discs we almost 15Ē and the front discs were around 14Ē. Which makes me think I got the max tow package? The standard brakes are supposed to have smaller discs in the rear.

esminbritt 05-11-2019 10:15 PM

Quote:

Originally Posted by lpennock (Post 28976909)
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"

Sent from my SM-T350 using Tapatalk

Is there any way I can verify this. Iím not doubting you. But Iím getting mixed info from Ram. I talked to someone at MOPAR and even they didnít know if it was Torsen or clutch. A senior MOPAR Tech is supposed to get back to me. 3 dealers told me that it requires additive which would tell me itís clutches. I donít mean to obsess, but I find it odd that AAM doesnít even list a 12Ē yet. Iíve never had so much trouble getting basic info on a pig before

KhakiCummins 05-12-2019 12:44 AM

Quote:

Originally Posted by esminbritt (Post 28978959)
Is there any way I can verify this. Iím not doubting you. But Iím getting mixed info from Ram. I talked to someone at MOPAR and even they didnít know if it was Torsen or clutch. A senior MOPAR Tech is supposed to get back to me. 3 dealers told me that it requires additive which would tell me itís clutches. I donít mean to obsess, but I find it odd that AAM doesnít even list a 12Ē yet. Iíve never had so much trouble getting basic info on a pig before

Easiest way to verify without any uncertainty is to pull the diff cover and look.

esminbritt 05-12-2019 09:51 AM

I wouldnt mind doing that but I normally change diff fluid at 1k for break in. It seems like someone must know for sure what it is. It's a 12" rear diff. No company has ever used such a large diff in a light/medium truck before. The mystery of this seems unnecessary. Somebody knows this.

Don_T 05-13-2019 08:15 AM

Just to help keep the water muddy, this is from the ownerís manual for the Ď19 2500/3500 I have with my new truck.

We recommend you use SAE 75W-85 HD Ram GL-5
Synthetic Axle Lubricant in 9.25 Front & 11.5 Rear Axles. Use
Mopar Synthetic Gear Lubricant SAE 75W-140 (MS-8985) in
12.0 Rear axles. Limited slip additive is required for limited
slip axles.

The only way to know for sure is as already posted, pull the cover and look at it.

EMCIcummins 05-13-2019 08:48 AM

my 2019 dually with the max tow package is 8x200mm wheel pattern

esminbritt 05-13-2019 09:15 AM

Quote:

Originally Posted by Don_T (Post 28979843)
Just to help keep the water muddy, this is from the ownerís manual for the Ď19 2500/3500 I have with my new truck.

We recommend you use SAE 75W-85 HD Ram GL-5
Synthetic Axle Lubricant in 9.25 Front & 11.5 Rear Axles. Use
Mopar Synthetic Gear Lubricant SAE 75W-140 (MS-8985) in
12.0 Rear axles. Limited slip additive is required for limited
slip axles.

The only way to know for sure is as already posted, pull the cover and look at it.

Yeah. i read that too. Doesnt really help much. I gotta use the 75/140 but the rest is still vague.

Jtekt 05-14-2019 09:14 PM

"Is it a torsen style clutch system?"

The TORSEN Limited Slip mechanism does not employ clutches. it is a series of helical gears arraigned to provide a lock up of both axles after one or the other side slips.

To further clear the air the AAM axles have never had a TORSEN unit in them! The unit in the AAM axles is an internal AAM design.

This comes directly from the VP of sales for TORSEN. This topic came up some time back and since I work for the parent company of TORSEN, I asked.

esminbritt 05-14-2019 09:30 PM

Quote:

Originally Posted by Jtekt (Post 28981351)
"Is it a torsen style clutch system?"

The TORSEN Limited Slip mechanism does not employ clutches. it is a series of helical gears arraigned to provide a lock up of both axles after one or the other side slips.

To further clear the air the AAM axles have never had a TORSEN unit in them! The unit in the AAM axles is an internal AAM design.

This comes directly from the VP of sales for TORSEN. This topic came up some time back and since I work for the parent company of TORSEN, I asked.

I knew Torsen didnít use clutches. So the AAM differential in the AAM axle uses what design? Helical gear or Viscous? I opened the cover today and it does not have clutches. I think people refer to the AAM as a ďtorsen-style.Ē Iím guessing they mean helical geared style.

cerberusiam 05-14-2019 09:47 PM

The AAM TracRite LS is a helical gear design with not clutches but rather brake shoes to control the TQ bias. You really want to use the recommended fluid and not try to mess around using others, results may not be as expected.

Jimmy N. 05-14-2019 09:56 PM

Quote:

Originally Posted by esminbritt (Post 28981369)
I opened the cover today and it does not have clutches.

If you shared a photo of what you found in there it'd be most helpful.

esminbritt 05-14-2019 10:17 PM

1 Attachment(s)
Quote:

Originally Posted by Jimmy N. (Post 28981405)
If you shared a photo of what you found in there it'd be most helpful.

I tried to earlier but couldnt from my phone. Here you go

Jimmy N. 05-14-2019 10:23 PM

Thanks, but I can't identify the diff from that angle.

esminbritt 05-14-2019 10:26 PM

1 Attachment(s)
Quote:

Originally Posted by Jimmy N. (Post 28981449)
Thanks, but I can't identify the diff from that angle.

How about this one?

Jimmy N. 05-14-2019 10:29 PM

Okay, that I can work with.
May not have an answer this evening as there are quite a few to compare the looks of.

esminbritt 05-14-2019 10:36 PM

Quote:

Originally Posted by Jimmy N. (Post 28981459)
Okay, that I can work with.
May not have an answer this evening as there are quite a few to compare the looks of.

I would sure appreciate any help you can give. Never had so much trouble Identifying an axle before. There are no clutches. They advertise it as "anti-spin"(...Like saying the wheels have "rolling tires" on it) It has to be a viscous or a helical gear. But which one? It's probably an AAM trac-rite, but what series. It could be an electronically engaged LS (eLS). But I'm guessing it's more just standard Torsen-style (Not Torsen brand)

Jimmy N. 05-14-2019 10:40 PM

I seriously doubt that it's a viscous coupling. If it was electronically engaged it would have wiring going to it.
At this point my wild guess is a cone type.

esminbritt 05-14-2019 10:45 PM

Quote:

Originally Posted by Jimmy N. (Post 28981467)
I seriously doubt that it's a viscous coupling. If it was electronically engaged it would have wiring going to it.
At this point my wild guess is a cone type.

I'm not familiar with cone type. is that a helical gear? I also dont think it's is a viscous

Jimmy N. 05-14-2019 10:48 PM

Of course I can't remember what the cone type was called now, but it's not a gear setup, but cones as the name implies.

esminbritt 05-14-2019 11:00 PM

Quote:

Originally Posted by Jimmy N. (Post 28981473)
Of course I can't remember what the cone type was called now, but it's not a gear setup, but cones as the name implies.

In the cut out circle above the ring gear (oriented in photo) you can look in and see what appear to be smaller gears inside of the cylindrical housing (not the right term). But maybe those are cones? It is a new diff (12" is the largest to date on a modern production pickup) , so it could be a whole different differential system. They beefed up all other drivetrain pieces, so one would assume they went with a stout setup

Don_T 05-14-2019 11:22 PM

I can see what looks to me like a spider gear inside the carrier. It seems to have cross shafts 90* from each other for the spider gears in the case. I donít think it would have spider gears if it is a Torsten type differential. If it were an open diff it usually has less material on the case and the spider gears are easy to see. I wonder if there is a clutch pack in there?

seafish 05-14-2019 11:44 PM

IMO, one of the the important questions is whether or not this new larger axle with bigger brakes can easily be retrofitted into a 3rd gen 2500 ??

BTGreen 05-15-2019 12:39 AM

Quote:

Originally Posted by esminbritt (Post 28981453)
How about this one?

That's a standard clutch limited slip. Can clearly see a cross pin and spider gears. It's a side dump carrier, why it looks different than a typical limited slip carrier.

esminbritt 05-15-2019 06:47 AM

Quote:

Originally Posted by Don_T (Post 28981497)
I can see what looks to me like a spider gear inside the carrier. It seems to have cross shafts 90* from each other for the spider gears in the case. I donít think it would have spider gears if it is a Torsten type differential. If it were an open diff it usually has less material on the case and the spider gears are easy to see. I wonder if there is a clutch pack in there?

The dealer looked at the parts diagram and there are no clutches pictured or offered as a part.

Jhenderson 05-15-2019 08:14 AM

Not surprising seeing as AAM doesnít even list a 12 inch diff in any of its literature including parts diagrams.

esminbritt 05-15-2019 09:13 AM

Quote:

Originally Posted by BTGreen (Post 28981547)
That's a standard clutch limited slip. Can clearly see a cross pin and spider gears. It's a side dump carrier, why it looks different than a typical limited slip carrier.

I wonder why there were no clutches listed in the parts/service diagram.


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