AAM 11.5” Anti-Slip Rearend fluid change

[SyN]

JR: Many thanks for your input & reply.
I by No Means am I ever implying that I feel or think 75W-90 viscosity is inferior.
I only think for my climate/driving style/habits 75W-110 is best suited.

Redline gear lubes have the following viscosities:
75w90: 16.1 cSt KV100 (Recommended viscosity for my truck)
75w110: 20.9 cSt KV100
75w140: 27.7 cSt KV100

Amsoil gear lubes in the following viscosities:
75W-90 (SVG) 15.9 cSt KV100
75W-110 (SVT) 20.9 cSt KV100
75W-140 (SVO) 26.1 cSt KV100

Over 37yrs I have been brainwashed into the Film Strength religion. (Which is not a bad thing)
Truthfully my pump will be filled with 1qt RL-75W-90 (left over) & 3qts RL-75W-110 this combo will be pumped into my 11.5” after the FF has been sucked out.

Next service I’m thinking 3qts 75W-110 & 1qt 75W-140.

 

[Cummins12V98]

AMZ/OIL recommends if towing a lot or heavy to use the 75-110 on the AAM's.

60k at time of pics running 75-110 SevereGear towing 33-35k 1/2 the miles.

 

[AH64ID]

The quote at the beginning is a post I made several years ago after a long chat with AAM.

Yes he mentioned an impact on mileage, but that wasn't the basis for the fluid recommendation.

The size of the bearings, fluid capacity, etc is why 75w-90 was recommended for all users.

Dodge/Ram also specs better bearings than GM, which uses the same axle.

If you look back thru Dodge manuals the Dana axles were recommended to run 75w-140 for heavy towing, but that recommendation is long gone.

I tow often, thou not as heavy as Cummins12V98, and run 75w-90 and have no plans to change. My gears looks great, as does the fluid after 50K miles.

 

[sdeeter19555]

Last I knew class 8 trucks were still specing' xw90, long haul intervals run as high as 500,000 miles. Run what makes you comfortable but a good synthetic 90 is more than adequate for a 15k load.

And I'm not so sure any fluids on these trucks are spec'd for fuel mileage over longevity. First, they are excluded from cafe requirements given the gvwr. If they really were shooting for that I'm sure Ram would be pushing Cummins to approve the use of 10w30 in the 6.7. They've been using it in their larger bore engines for a number of years now.

One thing to keep in mind with a class 7/8 truck is the size of the sump and the size of the ring an pinion...apples to oranges, you have a lot more oil for cooling and shearing and you have a larger ring gear (more leverage/less effort across that gear tooth), it's just not a good comparison.

For what it's worth, I ran 85w140 Royal Purple in my 2004.5 for well north of 200k (on that single fill), and traded with just shy of 300k on the clock...the only issue I ever had with that particular 11.5AAM was a pinion seal leak that would come and go on a whim (it would leak for a couple months, then stop leaking for a while, then start back up for no reason). No I will caveat this by saying I did not tow hard often, but I did run sustained speeds for upwards of 20 hours at a time.

Mobil 75w90 made my particular differential whine, RP 85w140 made it quiet, there was no perceptible difference in operating temps or fuel mileage, and I tracked mileage for every tank of fuel and played around with a non-contact IR thermometer once upon a time.

At one point there was a recommendation from Dodge (I don't remember if it was from "Dodge" or one of the high volume Dodge Dealers that were well respected on TDR) about running 75w140 for heavy towing in the AAMs many years back (I had a copy of it from this very forum way back when)...this was separate of the TSM that recommended 75w140 in the Corp 9.25 for the 1500 that originally caused the 75w90/75w140 uproar.

From what I remember though, the 10.5 and 11.5AAM were meant to run 75w90 with frequent OCI (15k mile intervals specified by Dodge if memory serves). This was also confirmed by TDR members directly from AAM (although the Dodge OCI was not confirmed or recommended by AAM). I also want to remember this was about the same time Amsoil launched their 75w110 for the Fords and everyone that was on the fence over 75w90 and 75w140 had a good compromise.

Another thing to note is the 11.5AAM is essentially the same differential used in the GM counterparts and they had different OCI schedules than Dodge...

So I'm glad to see this conversation has never really went away!