Front & Rear Diff, What fluid?

[AH64ID]

OPERATION



When one wheel begins to spin the pinion gears on that side are forced toward the pinion brake shoes. The pinion brake shoes then cause frictional drag on the opposite pinion gears and the side gear. These friction forces transfer the power to the opposite wheel. Once the frictional forces are overcome, differentiation will occur. The torque will be continually biased by the frictional forces to the high traction wheel.





From the Dodge 2004 FSM, page 3-158, Rear Axle.

Yeah was reading that in the 05 SM last night... Considering that the AAM LSD and TT both have the same number of pinion gears the shoes must be where the tunable bias ratio comes from. . It's not quite a true clutch pack thou, and chatter would tell me that something was wrong if it was coming from the shoes. I would call them more of a "friction enhancer" than a clutch...



If you look at the attached photos you can see the shoes on the AAM and lack of shoes on the TT. . if you take the shoes away they are the same (Which is why I think it has to do with the tunable bias ratio)

 

[TKarnas]

I live in Hanover PA



I think I am going to assume its a 10. 50" rear, 9. 25" front. Going to put in 75w90 most likely what ever Advance has that is full synthetic and I will buy one container of adder for the rear if it chatters. Does anyone know how much of the adder to put in?

 

[AH64ID]

okay all... . Two dealers ran my vin and both told me 10. 50" rear and 9. 25" front. Both told me 75-90w fluid but disagree on the rear adder... . Is there a site I can confirm that the rear is 10. 50"?

Do you have a HO or SO motor? Which transmission? I though the 10. 5" was done in 03 for the diesel.

 

[steved]

okay all... . Two dealers ran my vin and both told me 10. 50" rear and 9. 25" front. Both told me 75-90w fluid but disagree on the rear adder... . Is there a site I can confirm that the rear is 10. 50"?

The additive is only for the semifloating 1/2 ton (read 1500 Ram) rear differential with a trac-loc. You do not need the additive per the FSM. I believe there was something dodge that indicated if the differential chattered to use additive.



It doesn't matter if its a 10. 50" or 11. 50", they require the same fluid. The volume required only changes slightly.



GENERALLY, if the truck is an SO (250HP) and auto, it could have the 10. 50AAM. The manual and the HO typically required a 11. 50AAM. There were some 04s that still had the 10. 50AAM... its not just an 03 thing.

 

[TKarnas]

I have the SO Auto so I am going with the 10. 50. . Thanks to all I greatly appreciate all the help.



I will be going with the full synthetic 4 qts rear and 2. 5 qts front.

thanks again

 

[REckard]

I have 71k and have changed my fluid twice with fair amount of towing. I use conventional gear oil. I just dont see the need. Haven't had a problem and the rear sounds good and LS works good.



I think syn is waste myself.

 

[steved]

I have 71k and have changed my fluid twice with fair amount of towing. I use conventional gear oil. I just dont see the need. Haven't had a problem and the rear sounds good and LS works good.



I think syn is waste myself.

To add to this, this design is no different than previous differentials... there are a lot of miles on Dana's and Corporate 10. 5s (the old AAMs in the GM) with nothing more than regular gear oil...



My neighbor has a 95 Chevy with 280k and a the oil in the 10. 5AAM has never been changed and he has towed a car trailer (with a car) at least twice a week for the past two years.



I think synthetics were used because they typically have better characteristics and generally protect better at extremes.

 

[amsoilman]

Hmm. . i'll have to look at that when I get home. . here is the AAM info page on it with a cut-away diagram. .

Good Info:

The site you provided, AAM, even states "friction Modifier" not required.

 

[steved]

While not required, there have been several people on this very forum that have benefited from LSD additive in the AAM axles... IIRC, it was first done by a Dodge mechanic for someone and then it spilled over to here.

 

[AH64ID]

To add to this, this design is no different than previous differentials... there are a lot of miles on Dana's and Corporate 10. 5s (the old AAMs in the GM) with nothing more than regular gear oil...



My neighbor has a 95 Chevy with 280k and a the oil in the 10. 5AAM has never been changed and he has towed a car trailer (with a car) at least twice a week for the past two years.



I think synthetics were used because they typically have better characteristics and generally protect better at extremes.

The AAM 10. 5 is not the same as the corporate 14bolt FF found under the chevies. .

 

[steved]

The AAM 10. 5 is not the same as the corporate 14bolt FF found under the chevies. .

A differential is a differential... they are all slightly different, but they do the same thing: transfer energy 90 degrees.



I only indicated these specifically because some of us have more miles on a Dana or Corp 14-bolt than any significant number of the newer AAM. I know of several Corp 14-bolts and Dana 60s (not even the stronger D70 or D80) that have 500k of hauling miles, and that only ever had oil added to them when a wheel seal was replaced... a far cry from the 15k interval specified by Dodge.



Differentials typically use the same bearings, races, and seals; and typically the same type of gear. Those are the only things that really matter. They did not change with the AAM, and since those differentials lasted hundreds of thousands of miles (abused miles), one could hypothesize that a newer AAM would provide similar service with nothing more than regular gear oil.



I only posted to provide some food for thought... not to compare the internal workings of one differential to another.



And FWIW, the Corp 14-bolt was built for GM by AAM...

 

[AH64ID]

A differential is a differential... they are all slightly different, but they do the same thing: transfer energy 90 degrees.



I only indicated these specifically because some of us have more miles on a Dana or Corp 14-bolt than any significant number of the newer AAM. I know of several Corp 14-bolts and Dana 60s (not even the stronger D70 or D80) that have 500k of hauling miles, and that only ever had oil added to them when a wheel seal was replaced... a far cry from the 15k interval specified by Dodge.



Differentials typically use the same bearings, races, and seals; and typically the same type of gear. Those are the only things that really matter. They did not change with the AAM, and since those differentials lasted hundreds of thousands of miles (abused miles), one could hypothesize that a newer AAM would provide similar service with nothing more than regular gear oil.



I only posted to provide some food for thought... not to compare the internal workings of one differential to another.



And FWIW, the Corp 14-bolt was built for GM by AAM...

I agree. . and those older (still used) Corp 14 bolt FF alxes are GREAT axles. . the one we have has 200K hard miles on it w/out so much as a cough... The Corp 14bolt SF we have/just sold had 200K hard miles on it as well. .



Yes the copr 14bolt is a AAM product, but its different than the 10. 5AAM used in the 2500 Hemi's.



Our front axle is the front/revamped version of the Corp 14bolt SF axle.



While its been proven they will work on old nasty fluid, I still prefer to change mine...

 

[brods]

Lol. Fwiw GM spun off its axle plants many years ago which were then turned into AAM. So the GM 14 bolt is the predecessor to the AAM axles. The die hard Mopar guys must hate driving around on these AAM *******ized chevy axles.



Tkarnas, don't sweat it, just follow Steve’s advice:

75w90 in a quality synthetic will be fine... everyone has their favorite. Run a name brand and you should be fine... these differentials aren't as delicate as Dodge seems to indicate in that 15k change schedule.



Nix the synthetic blend. Just buy a full synthetic... Mobile 1, Amsoil, Royal Purple, Redline, even Lucas offer full synthetic gear oils. Dodge lubricant specified in the 2004 FSM:





REAR AXLE



10 1/2 AA - Mopar Synthetic Gear Lubricant 75W-90



11 1/2 AA - Mopar Synthetic Gear Lubricant 75W-90



NOTE: Trac-Lok differentials require Limited Slip Additive in the lubricant. Trac-Rite™ differentials DO NOT require Limited Slip Additive.







Nix getting the LSD additive, I would only buy it if you find its needed (ie you get chatter). Most synthetic gear oils already have some LSD additive in them. As noted above, the Trac-Rite does not require it.



The FSM indicates 4. 75 pints (2. 5 quarts) for the front 9. 25AAM and 7. 65 pints (4 quarts) for the rear 11. 50AAM. I would buy at least one, if not two, extra because they always seem to hold more than indicated.



Where in PA are you located??

If you change the oil yourself (its easy), don’t forget to clean the dirt out of the gap between the top of the cover and the axle housing with a hard bristle brush or something similar and flush it good with some cleaner before you start. If you don’t then when pulling off the cover the dirt trapped up there will fall on the ring gear.

 

[TKarnas]

Again thank you all for your help... this is a great site and the membership pays for itself ! You all are the best and thanks

 

[amsoilman]

The requirements for automotive gear lubrication have changed over the years! There are several forces driving the need for better gear lubrication.



First is improved fuel economy. Modern Vehicle aerodynamics, with lower level air dams like our trucks have, is decreasing the air flow over differentials, which increases the operating temperatures.



Also, lubricant fill volumes have been reduced in order to lower fluid drag on gears and bearings for further improvement in fuel economy. All differentials are dependant on the fluid within to cool the components inside, so with less fluid capacity, operating temperatures rise. I have seen tests with 5th wheels behind 1 ton trucks pulling grades of 3. 5% grades, where the temperatures have been recorded as high as 370 degrees F.



As we all know, each and every new model of our trucks gain in HP as well as hauling and pulling capacity, which puts more demand on the gear lube in the differentials.



In the case of many vehicles, creature comforts have demanded greater interior space, forcing the manufactures to lower floor boards, which again restricts ar flow to the differential. And in many cases, the HOT exhaust pipes have been forced closer to the differentials, which again increases the operating temperatures of the differental.



Just for the fun of it, after you make a hard pull in your trucks, go out and see if you can place your hand on the differential without burnig it... ... ... ... ... ... ... ... ... ... ... . bet you won't hold it there long!



wayne

 

[REckard]

You can always count on the amsoil distributors to scare someone into thinking synthetic lubes will save the world.



I love it. Replying to a post and sying a dino lube has been working fine is like sort of like fishing. :-laf

 

[amsoilman]

You can always count on the amsoil distributors to scare someone into thinking synthetic lubes will save the world.



I love it. Replying to a post and sying a dino lube has been working fine is like sort of like fishing. :-laf

Where in my post did I say anything about Synthetics?



Wayne

 

[steved]

The die hard Mopar guys must hate driving around on these AAM *******ized chevy axles.

I don't, AAMs have an excellent reputation... as good as any Dana product.

 

[brods]

Sorry but I disagree with that. I'd trade this front AAM axle for a kingpin D60 in a heartbeat!

 

[steved]

Even the later Dana's didn't have a kingpin... they lost that in 94. Kingpins aren't the answer... they have their inherent issues too...