typical oil temps on the 11.5 american axle?

[The motor guy]

I'm trying to determine a good oil weight to use for this differential. I changed out the factory fill at 15,000 and put in the called for 75w90 oil. I used amsoil. Well I'm at 30,000 miles and it's due for another change. Does anyone have any idea as to what temp this diff runs at usually? I've heard some say it's a cool runner and others say it get so hot the paint burns off. Which every other dodge Ive seen with this diff has the same issue. I'm thinking of pulling a sample to see how far I can run this fluid. Changing every 15,000 is ridiculous. I am throwing around the idea of putting some amsoil 75w110 in their but I want to see what the operating temps are first. I live in houston where the temps are around 90-100 degrees for 6 months out of the year. It can get to 110 around august.

 

[disturban]

15k is stupid and even 30k is a waste especially running Amsoil or any other synthetic. I changed my diffs at 80k running dino lube and they are just fine with 160k on them now, these are 10bolts that are a lot weaker than your ring and pinion and I tow and off road a lot. There are many vehicles on the road with 200 and even 300k on them that has never even had the diff fluid changed!

IMO extreme severe duty such as towing over 10,000lbs every day change it at 50k and normal driving every 100k and I bet the farm you never have an issue because of the fluid.

 

[mechtech2]

Sometimes the factory recommends changing the rear end lube early.
No, it is not normal to change it at 15-30k.
They must have some reason.
I would lean in their direction.
Of course, use a full synth.

 

[The motor guy]

I'm gonna see how long I can run this gear oil. I'm gonna send a sample in on the 15,000 i have on now and go from there. I'm not going to change it every 15,000. I'm trying to cut maintenance costs on this vehicle. Hopefully I can get up to a more reasonable 50,000 miles.

 

[Jim Allen]

Originally Posted By: motor_oil_madman
I'm gonna see how long I can run this gear oil. I'm gonna send a sample in on the 15,000 i have on now and go from there. I'm not going to change it every 15,000. I'm trying to cut maintenance costs on this vehicle. Hopefully I can get up to a more reasonable 50,000 miles.


Good thinking! A UOA will tell the tale as far as the oil goes, but like Mechtech said, there's some reason for the 15K recommendation so it isn't wise to ignore it willy-nilly. Perhaps it's based on some lousy factory fill oil and you'll find that out. In any case, tread lightly, as your good instincts indicate, and you can see how far to push the recommendation based on informal field tests.

Also, you might invest in a diff oil temp gauge, which will tell the tale from the temp aspect. I know AutoMeter and Isspro have them. With the cover off, you can braze in a bung (AutoMeter has them) and install a sensor into the original cover. Probably not a bad idea if you plan to work the truck anyway. Then, you could tell us all about 11.5 diff temps! Or get a finned cover that has a built in port such as the MagHytec, whicn will also increase oil capacity by several quarts).

I have a nagging suspicion that the 15K recommendation may be based on running a 90 grade when the diff really wants a 140 when it's being worked hard. If the 90 is being cooked, then it would need to be changed more often. The lower grade oil helps with MPG and that could be their reasoning. For a lot of folks, who never really work their trucks, the 90 grade would be fine... even if not changed at 15K. For those that work them, 15K OCIs would be vital if they are running at high temps often. By recommending the short interval, they deal with that AND can brag about MPG at the same time. Pure speculation on my part but.... it's a thought.

 

[The motor guy]

Here is a uoa that D-Roc posted in another thread. Hopefully he doesn't mind me using it. He's got an 06 dodge ram with the same 11.5 american axle I have in my truck. This is 75w90 gear lube. How are these numbers for wear? I'm not really familiar with gear oil uoa. I don't know what is considered good wear or bad wear. Oh this was a 15,000 mile interval.

Na 6
K 1
Si 4
Al 1
Fe 88
Cr 0
Pb 0
Cu 0
Sn 0
Ni 0
Ag 0
Ti 0.13
V 0
Zn 26
Ma 1
Ca 11
B 0
Mo 42
P 1033.8
V100 14.9
V40 100.4
Water T 0.1%


ISO 23/17
5uM 51285
10uM 11853
15uM 766
20uM 14
30uM 71
50uM 3
75uM 1
100uM 0

 

[Jim Allen]

That's an outstanding report. Very low iron, great ISO Code info (23/17 is good compared to the few other gear oil tests I've seen... you dont't often see it done on gear oil), and still well in grade. Do you know if this report was the factory fill? He didn't get oxidation or TAN, which would have been useful too. The oxidation would show how hot the oil runs... ie running hot all the time will yield a higher number. If he did it at Blackstone, I don't think they can do oxidation. If I recall, DRoc tows with his truck, so a lightly used unit might read even better.

FYI, the first gear oil change change is the most important due to break in, so I'd advise 15K (or less) for the first to clear out all the break in junk and monitor from there. In other words, if you test the factory fill oil, expect to see more metal than normal. You can still look at viscosity and oxidation to get an idea of what's going on but, IMO, UOA of the factory fill is not worth the money because it doesn't tell you too much that's useful... skewed by the break-in. Even the oxidation might be high because the R&P will run lots hotter than normal while it breaks in.

 

[deeter16317]

Originally Posted By: Jim Allen


Good thinking! A UOA will tell the tale as far as the oil goes, but like Mechtech said, there's some reason for the 15K recommendation so it isn't wise to ignore it willy-nilly. Perhaps it's based on some lousy factory fill oil and you'll find that out. In any case, tread lightly, as your good instincts indicate, and you can see how far to push the recommendation based on informal field tests.

Also, you might invest in a diff oil temp gauge, which will tell the tale from the temp aspect. I know AutoMeter and Isspro have them. With the cover off, you can braze in a bung (AutoMeter has them) and install a sensor into the original cover. Probably not a bad idea if you plan to work the truck anyway. Then, you could tell us all about 11.5 diff temps! Or get a finned cover that has a built in port such as the MagHytec, whicn will also increase oil capacity by several quarts).

I have a nagging suspicion that the 15K recommendation may be based on running a 90 grade when the diff really wants a 140 when it's being worked hard. If the 90 is being cooked, then it would need to be changed more often. The lower grade oil helps with MPG and that could be their reasoning. For a lot of folks, who never really work their trucks, the 90 grade would be fine... even if not changed at 15K. For those that work them, 15K OCIs would be vital if they are running at high temps often. By recommending the short interval, they deal with that AND can brag about MPG at the same time. Pure speculation on my part but.... it's a thought.




The last I knew, the 2500/3500 trucks were not considered part of the CAFE number, so why would the manufacturer care what mileage they yielded? The oil grade recommendation of 75w90 is directly from the axle builder, AAM.

For the record, the 15k interval is severe duty while normal everyday use is a no-change interval. From a discussion I had on a GM forum (this is the same axle used in the 2500/3500 GM trucks), GM recommends a 50k OCI.

 

[Ken2]

The short drain interval and great heat in some differentials is due to either under-spec'ing the differential to save cost & weight (almost too small & light duty), or sloppy assembly at the factory. If yours runs normally warm and looks good, not black & cooked, you might try longer intervals. And, stepping up to 110 or 140 weight in your climate seems smart.

 

[The motor guy]

In his post he said he had the bearings replaced at 140,000 miles. He didn't say how many miles were on unit all together on this report but he did say it was 15,000 miles on this fill. I guess he replaced the bearings but left the original ring and pinion in there.

 

[Jim Allen]

Originally Posted By: deeter16317

The last I knew, the 2500/3500 trucks were not considered part of the CAFE number, so why would the manufacturer care what mileage they yielded? The oil grade recommendation of 75w90 is directly from the axle builder, AAM.

For the record, the 15k interval is severe duty while normal everyday use is a no-change interval. From a discussion I had on a GM forum (this is the same axle used in the 2500/3500 GM trucks), GM recommends a 50k OCI.


Good info! The 15K interval makes sense in light of severe service. This 15K thing has come up several times on this axle but you've put it in context. RTFM! So, the OP gets his answer... err... rather it was in his owners manual. ( : < ): No mileage limit in light duty service.

 

[The motor guy]

They actually took out the unlimited mileage part out of my owners manual. The only schedule now is every 15,000 miles for some reaseon. More money for chrysler I suppose.

 

[deeter16317]

Hmmm, every manual I've seen up to 2007 had two schedules...schedule A and schedule B. One was 15k the other was not listed (no change interval).

You must have a newer truck...

 

[deeter16317]

Ahh, now that I'm looking at the forums online (not via smart phone), I see you have a 2007.5.

One thing to note is that it has been mentioned on other forums that the short OCIs is based on the use of the Trac-Rite LSD unit and its supposed habit of shedding particles.

Personally, I have had only two ugly looking OCIs on my 11.5AAM: the first on the dirty OE fluid at around 50k and the second around 75k on a "burnt" fill of 75w90 Mobil 1. I did a short change on 75w90 Royal Purple, then swapped in 85w140 for the next 100k+ (single fill, 100k+ miles on it). I recently changed to Schaeffers 75w140 around 220k, and the RP I drained didn't even lose its purple color in that time in use, nor did the magnet have any notable debris on it. I sit with right about 255k on the unit.

As I previously noted, AAM specifies 75w90, even if you contact them directly; they will tell you the 11.5AAM needs nothing more. I do know that several "garages" recommend 75w140 if you tow heavy, but that isn't a TSB from DCX. Personally, after my experience with 75w90, I won't run anything less than 75w140.

One thing I have found is that, regardless of DCX's claim that no LSD additive is needed, some gear oils need the modifier added...Schaeffers caused LSD chatter, and it took two 4oz bottles of Mopar LSD additive to quiet that down completely.

I still highly doubt the need to change every 15k. I do not follow that recommendation either, as the AAM is no different than the previous Dana or even the classic 10.5AAM used by GM for almost 30 years...and you didn't see rash failures of them.

 

[The motor guy]

im gonna see how far I can go with the amsoil 75w90 in it right now. Deeter did you run 75,000 miles on the mobil one fill that you burnt or was it 25,000 miles? Im hoping to get atleast 50,000 miles out of it. Cause changing every 15,000 miles ends up being around 500 dollars per 100,000 miles. I'd rather try to cut costs and just put the money into a rebuild when the time comes.

 

[deeter16317]

Originally Posted By: motor_oil_madman
Deeter did you run 75,000 miles on the mobil one fill that you burnt or was it 25,000 miles?



I only got 25k out of the "burnt" Mobil 1 fill...and to elaborate, the reason I changed so soon was the fact the differential had become noisier than normal and when I drained the fluid, it was dark brown and smelled burnt, and I want to remember it drained very fluid-like (thinner than a 75w90 should have been). Here are my approximate OCIs:

Factory Fluid to 50k.
Mobil 1 75w90 to 75k.
RP 75w90 to around 100k.
RP 85w140 to around 220k.
Current fill of Schaeffers 75w140, sitting at 255k.

For the record, I changed the front differential at the same time as the rear with Mobil 1, and I still have that same fluid in use (although I have lockout hubs, so the front parts don't turn that often)...its still crystal clear with many years on it.

 

[NavyDood]

The 15,000 mile heavy towing use drain interval that Dodge recommends for the AAM 11.5" axle is absolutely retarded, so is the 30,000 mile normal use schedule. GM trucks with the Duramax use the same 11.5" AAM axle that Dodge uses. GM says there isn't a scheduled OCI if you use a "real" synthetic.

I changed my dif fluid about a month ago. I had the regular Amsoil Synthetic 75W-90 in it for five years and had just over 100,000 miles on it. Next fluid change will be in another 100,000 miles.

 

[NavyDood]

Here's some add-on info. I am running the regular Amsoil synthetic 75w-90. Not the Severe Gear. I just towed my 12,000lb fifth wheel from MD to TX going the northern route through IN averaging 65mph. When I got further south into AR and TX, the highest outside temp I saw was 106°F. When I checked the temp of the differential with my infrared gun in AR and TX at fuel stops, the highest temp I saw was 184°F.

 

[The motor guy]

Good to know. You can probably add 20 degrees to that temp since the fluid would be hotter than the cover because the cover is exposed to air.