AAM 11.5, carrier gears damaged

[mpaulson]

I serviced the rear diff today and when I pulled the drain plug. the oil was black and the magnet had chunks of gears on it. So I pulled the pan and it is the gears in the carrier, they are chipped. The ring and pinion are fine. What the heck would have caused this? I have had not signs of anything being wrong, no noise, odd feelings or anything. I know the oil wasn't low because I checked the level last weekend while servicing other items. I change the oil every year and it has been Amsoil 75-140 since the first time that I serviced it after it was new. Anyone had this before? I found one in a serch from back in 2004 or so, but no reasons for this. I'm not looking forward to Monday when I find out what this will cost.

 

[HBarlow]

I've put lots of miles on one Dana in a Gen II and also on two AAMs in Gen IIIs. Haven't seen or heard of differential failures like that.

I don't know much about differentials but it is odd that the gear (isn't that the pinion gear?) that meshes with the ring gear is badly damaged but no damage is showing on the ring gear.

It might not be that bad. Probably $500 or less.

 

[NIsaacs]

Wow thats ugly! I am not familiar with AAM axles, but that looks like one of the axle gears, which meshes with the spider gears which is part of the locking system/limited slip?



Looks like shock damage or faulty metal.



Nick

 

[steved]

That's one of the spiral gears that operates the LSD...

Never seen that before, I wonder if there's a clip or something that fell out and got run around in there... similar to the Dana's issues?

 

[mpaulson]

As far as I know, these gears only move while turning corners, and I'm usualy light on the throtle if I use it at all while I am turning with a load. Going straight ahead, they should not be moving. Now that I've thought about it, I think that I have had a sign of this happening. There is one corner by my shop that occaionally I felt something odd that I thought may have been the front wheel bearings groaning under the side load of turning, but now I'm sure it was the diff grinding these gears in the turn. I hope it is a simple as pulling the carrier out and replacing the small gears and checking all the other bearings for damage. I've sunk enougth money into the truck this month upgrading other parts. I just finished installing the EMS free spin kit about an hour before I made this discovery and I have a Borgeson box and BD steering stablizer on the way also right now and just did the shocks. #@$%!

 

[steved]

The center chunk is not serviceable, and will need replaced as a unit.

 

[llotton]

Aam gears

If I am ever faced with having to replace the entire center section on the AAM 11. 5 in my truck I will go to the "True Trac". Just my two cents worth.

 

[AH64ID]

The true trac is a better unit, but being a helical gear design it will still have the same shortcomings with traction issues when taking off from a stop.

 

[TCDiesel]

The true trac is a better unit, but being a helical gear design it will still have the same shortcomings with traction issues when taking off from a stop.

No way My True Trac and everyone one I have install out perform the AA LSD in every traction category,it is somewhat snaky in tight spots when slippery. It not often ,But I've seen the gear(s) chew up before.

 

[TCDiesel]

As far as I know, these gears only move while turning corners, and I'm usualy light on the throtle if I use it at all while I am turning with a load. Going straight ahead, they should not be moving. Now that I've thought about it, I think that I have had a sign of this happening. There is one corner by my shop that occaionally I felt something odd that I thought may have been the front wheel bearings groaning under the side load of turning, but now I'm sure it was the diff grinding these gears in the turn. I hope it is a simple as pulling the carrier out and replacing the small gears and checking all the other bearings for damage. I've sunk enougth money into the truck this month upgrading other parts. I just finished installing the EMS free spin kit about an hour before I made this discovery and I have a Borgeson box and BD steering stablizer on the way also right now and just did the shocks. #@$%!

I doubt it will be that simple ,,You will need a new Diff and bearing kit. . the R&P may be good but any sign of damage I would replace it all.

 

[AH64ID]

No way My True Trac and everyone one I have install out perform the AA LSD in every traction category,it is somewhat snaky in tight spots when slippery. It not often ,But I've seen the gear(s) chew up before.

I don't disagree it's a better unit, just stating that the Achilles heel of helical gears is when one wheel is stopped. They are the best for icy conditions thou, its why despite a few downfalls I think the AAM is the best OEM LSD, at least its better than the handful of others I have owned/driven.

 

[TCDiesel]

I don't disagree it's a better unit, just stating that the Achilles heel of helical gears is when one wheel is stopped. They are the best for icy conditions thou, its why despite a few downfalls I think the AAM is the best OEM LSD, at least its better than the handful of others I have owned/driven.

Ok. . I see Your Point. . I have had several lockers . . The true trac is my preferred Diff for every Day and light commercial use.

 

[JMarketos]

my condolences. That type of damage does seem rare- will be interesting to learn if the cause can be diagnosed further on disassembly. Hope not too pessimistic, but I'm going to come on the other side of this one- "that not look cheap". The differential gears move more often than you might think. About the only time they don't move is on a very straight line down the highway. Even when going around a curve at highway speed, they move slowly. (That's if the L/R tires are inflated same. ) If it's any consolation, this appears to be the type of damage that might have blossomed as the metal fragments got into other stuff and bigger pieces came apart- good thing you happened to catch it as you did, else it would probably have caught you somewhere in the future, when you least expected it... Kudos for active routine maintenance. You have me thinking I need to change my axle oils now... Best of luck to you.

 

[mpaulson]

According to the Gear Centre here in Edmonton , a local Detroit distributor, the Tru trac is exactly the same as the oem unit. They come from the same factory. I'm getting the tru trac for $488 Canadian. From what they say the oem is made by Detroit.

 

[AH64ID]

The OEM is made by AAM and the TT is made by Detroit, and they are not one in the same. Detroit is a division of Eaton, who is one of AAM's competitors.





$488 CDN is awfully cheap for a TT, they should be closer to $750 CDN or more, hopefully he didn't order you an OEM one.

 

[dieselpowered]

Mine did that at 4000 mi. Replaced under warranty. Eaton is finally making a detroit locker/ NO Spin should be out in a few months. Randys Ring and Pinion has the part #. I know people will say its harsh, but I swear buy them.

 

[mpaulson]

Yep, called the guy back to ask a few questions, and that was an open one!#$#@ Now I'm at $1385 for the detroit true trac unit. I can get a Yukon Grizzly for $1015 locally but I'm going to go with the True trac one based on the opinions that I have read and heard. both of these units are in stock here, so by the time I ordered one in and paid the shipping, I would be no further ahead $$ wise and I don't have time to wait. The oem one is $1080 at one of the local dealers.

 

[DGamelin]

Mine went bad at 55k, it was replaced under warranty. If I was spending my money I would go with a plate type. Helical types are useless in snow. It is also very important the oil gets changed every 15k with helical because of the way they work, they make a lot metal filings and that shortens bearing life. We just put an OX locker in the front of a custom axle. What's neat about them is you can turn them off and on, but they're really expensive. We have a commercial account that just got 2011 fords with electric diff lock rears, really slick. Good luck.





________________________

93 250 2wd XC 354 auto

04. 5 3500 4wd CC dully 373 6-speed

 

[AH64ID]

If I was spending my money I would go with a plate type. Helical types are useless in snow.

I have the opposite belief. I have never had a better snow traction with a plate style, as long as your not stopped.

 

[DGamelin]

For us it's a matter of getting the load moving. When you spend the time to load and tie down a tractor or whatever, get in the cab and have only one tire in front and rear spin no matter how hard you spin them it pisses you off having to unload the machine and push your truck, reload and try it again. The helical will not give you posi unless both tires have some traction. They're design was intended to behave better at highway speeds, it is much harder to make the rear end come around then with a plate type. Dodge advertised this at one time as a safety item. The helical type posi is what they put in big trucks, it allows more give and less tire wear. If you lift one tire off the ground the truck will not move, a plate type will. I dont like driving a plate type on icy roads. I guess it just depends how much posi you need or want.