11.8 / 300mm AAM Rear Axle Fluid Change

[gsbrockman]

On January 11th I changed the rear axle fluid in my '13 RAM 3500. It's currently at 36,729 miles and 720 hours. I've performed a decent amount of towing....some light, some medium, and some teetering on heavy.

On my previous two RAM's with AAM axles, front and rear axle fluid changes were a breeze due to the reusable gaskets. The 11.8 / 300mm is no different. The only difference is that the attaching bolts on previous models held the differential cover on with 13mm bolts. The aluminum rear cover on the 11.8 / 300mm requires a Torx / External Star style socket in the size E10. No fasteners on any of my previous automobiles have ever utilized this style fastener, so I had to purchase this one for the ol' toolbox. For ever what reason, there's two bolts counterclockwise of the "12 o'clock" bolt that are stud like in nature that require a 13mm socket.

I began by driving the truck around to the tune of about 14 miles. I wanted to change it the previous evening, but by the time I ran some errands, it was getting dark and I wanted to take pics and share with anyone else on here that might have been interested. Everything went well with no issues. I used some brake parts cleaner to clean up the pan. I was actually quite surprised to see the minimal amount of shavings stuck to the magnet on the rear cover. As expected, the fluid was dirty, but still smelled as good (?) as the new fluid I installed.

External Star Socket in 3/8" drive in size E10.
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Shot of rear axle with reusable gasket still stuck to housing.
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Inside shot of aluminum cover.
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Outside shot of aluminum cover.
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Part number on aluminum cover.
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I cleaned up the rear cover, housing, and reusable gasket with the brake parts cleaner. I cleaned the threads of all the bolts (they may have had some type of thread lock on them) and re-installed. I drained out almost 7 pints of dirty fluid; I installed about 4 full quarts. I'd purchased 5 quarts as I was unsure if the rear cover added any capacity or not. If it does, perhaps it's offset by the slightly larger 11.8 ring & pinion versus the 11.5 ring & pinion; I'm sure the difference is negligible.

Reusable rear gasket.
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About 1/2 of the old fluid in a plastic container. It looks dirtier in the container than on my fingers.
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Old fluid on a paper plate for reference.
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Rear aluminum cover magnet with shavings.
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I purchased Valvoline 75W90 Full Synthetic in GL5 (part number VV975). I purchased 5 quarts but only used 4 quarts.....the front differential will get changed soon.
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[Gonzo 1066]

I have been changing Diff oil in my AAMs at about 30,000 miles of hard towing. Usually the oil looks just like what you drained the first change and then a bit better the next changes. I assume that this is due to the gears wearing in. Thanks for the informative post.

 

[JR]

Good lord, how many miles do you put on a truck in a years time if you already have 36k on your 13??

 

[gtoli]

Thanks for the info and pics.

 

[gsbrockman]

Good lord, how many miles do you put on a truck in a years time if you already have 36k on your 13??

I guess we'll find out May 31st, 2014 when it has its First Birthday.

 

[6speed]

If my calculations add up right he should have about 54,000 by the time it turns a year old. Then it will be good and broke in.

 

[6speed]

And the way he is driving it, he is averaging about 51 MPH. I'm only averaging about 36 MPH and most of my time is freeway.

 

[gsbrockman]

And the way he is driving it, he is averaging about 51 MPH. I'm only averaging about 36 MPH and most of my time is freeway.

You're all over it like a duck on a June bug.....last I checked, it was about 51.2 average MPH.

 

[6speed]

I like it when I guess dead on or damn close. Are you a hot shot? There is definitely no idle time at an average like that. And if my calculations are on your doing about 4500 a month. When I drove big trucks I was only doing about 10k a month. 98% of those days were dedicated runs of about 160 miles round trip 3X a day.

 

[Cummins12V98]

I like the aluminum cover but it does not look like they add much capacity over the steel covers. I will be taking my MagHytec cover of my 11 and installing on my future 14 or 15 later this year and nearly doubling the capacity.

 

[gsbrockman]

I like it when I guess dead on or damn close. Are you a hot shot? There is definitely no idle time at an average like that. And if my calculations are on your doing about 4500 a month. When I drove big trucks I was only doing about 10k a month. 98% of those days were dedicated runs of about 160 miles round trip 3X a day.

I took delivery June 1st.....looks like it's 7.5 months old (231 days). There's only two hours idle time and 752 drive hours showing on the EVIC. I'm currently at 38,380 miles.

 

[Learjet]

old thread...but I just changed my rear gear oil today. 1st change at 21,000 miles with 1/2 of those miles towing my 12,000 lbs 5th wheel. Magnetic looked just like the pictures above, teeth had a perfect wear pattern and oil seemed to be better than pictured above. I should have sent a sample to Blackstone, maybe next time. I'm thinking I will go a little longer next time...maybe 30,000 and send in sample.

Oh!...this think needs a drain plug...kind of a pain in the %^& pulling the cover.

for a tip...I bought a pump...but didn't use it. If you squeeze each bottle in the hole as much as you can get in easily, then after all 4 bottles... take the three bottles and empty into the last bottle (4th one) you can fill it easily and quickly without a pump.

2nd tip...a bright flash light you can see the level inside the diff.

 

[Cummins12V98]

Learjet, I highly advise NOT going any longer especially if you are using the OE I TRIED TO BY-PASS THE CUSSING FILTER. I did send a sample in on my OE lube and it came back as completely toasted!!! I was experiencing grabbing when taking off on a turn towing.

 

[Learjet]

I used Mobil 1 75W90 Full Synthetic - GL5. It's kind of odd that GM uses the same AAM axle and doesn't specify a replacement schedule...Like Ram does.

 

[Cummins12V98]

Here is my report for the OE rear diff fluid.