AAM 11.5” Anti-Slip Rearend fluid change

[SyN]

Question: For those with this specific rearend who tow regularly med/heavy loads.
When it’s time to do the routine service of this unit are you going to stay with the Recommended not Required 75W-90 viscosity?
Or
Switch to a heavier viscosity such as 75W-110 or 75W-140?

Thanks

 

[GrantP]

I switched to 75w-140. I think the 75w-90 recommendation is more for fuel economy rather than longevity. My .02

 

[Learjet]

I wish I could find the letter from AAM saying NOT to run 75w-140 in the 11.5 or 11.8 axle. Someone has it???

Here is quote from another website:

"Actually its not recommenced for any of the AAM HD axles, by Dodge nor AAM. I have called to and spoken with AAM about their 11. 5" axle. That axle and gears were designed to operate on 75w-90 under 99% of operating conditions. The engineer told me that unless you tow well above GCWR thru Death Valley in the summer that there is no benefit to 75w-140, infact it will detract from your mileage. "

 

[SyN]

My question is: How can the design of the metal gears be specifically designed & created to operate on only one specific viscosity of gear oil.
Please don’t attempt to convince me it’s the special clearances & tolerances.
That has been proven BS.

I know of a handful of Ram owners who are running a heavier viscosity compared to the recommended 75W-90 for many years while towing & no issues.

All I have found so far is the recommended viscosity is for better MPG .
Not one statement: Claiming less wear & increased longevity compared to heavier viscosity gear oils.

 

[6V92TA]

I wish I could find the letter from AAM saying NOT to run 75w-140 in the 11.5 or 11.8 axle. Someone has it???

Here is quote from another website:

"Actually its not recommenced for any of the AAM HD axles, by Dodge nor AAM. I have called to and spoken with AAM about their 11. 5" axle. That axle and gears were designed to operate on 75w-90 under 99% of operating conditions. The engineer told me that unless you tow well above GCWR thru Death Valley in the summer that there is no benefit to 75w-140, infact it will detract from your mileage. "

My question is: How can the design of the metal gears be specifically designed & created to operate on only one specific viscosity of gear oil.
Please don’t attempt to convince me it’s the special clearances & tolerances.
That has been proven BS.

I know of a handful of Ram owners who are running a heavier viscosity compared to the recommended 75W-90 for many years while towing & no issues.

All I have found so far is the recommended viscosity is for better MPG .
Not one statement: Claiming less wear & increased longevity compared to heavier viscosity gear oils.

see the highlighted answer above

 

[BLNRAY]

440,450 on mobil 1 75-90w,think i'll stay with the recomended oil

 

[SyN]

Grant: At this point & time I tend to agree!
Ray: Do you tow med/heavy loads for long periods of time?
My new Ram will tow mostly during the spring/summer/fall months: 12K-14Klbs.

I’m not here to start another recommend or (required) oil viscosity debate.
I only would like to get to the root of WHY the 75W-90 is recommend for THIS specific gear set. The axle housing itself has nothing to do with the recommended gear oil viscosity.

Like I already posted: So far I have only been told & read the 75W-90 was recommended only for increased MPG —->NOT lower wear #s & better longevity of the unit itself.
When I read this it reminds me again of (CAFE) government speak. And I by no means believe or trust anything the government attempts to tell us! (Our best interest is never a top priority)
& the government basically tells the automakers what they can or can’t do & its all about the MPG. (Which focuses on lighter viscosity oils throughout the Auto).

I have no issue running 75W-90 while towing med/heavy loads as long as I know it was (honestly/truly) my best choice of gear oil viscosity for this rearend.
When MPG seems to be the only priority I’m going to do some looking & searching around for better answers.
Trust has to be earned with me & the automakers & their partners (Government) has not done a wonderful job earning that trust over the last 37yrs. With Me!

Anyway: I was only curious which owners whom really work their Rams who have switched to the heavier viscosity gear oils.
I have already sucked out the FF (75W-90) after the Rams first towing adventure of 472 miles towing over 12K lbs & refilled with RL- 75W-110.
At the 10K mike mark I will replace the stock cover with a finned aluminum cover that incorporates a drain plug which will make draining & service much easier & faster.

I know the Rearend gear oil will run a bit cooler with the lighter 75W-90 (less friction). But more/faster shearing will occur while towing compared to the heavier viscosity. (So shorter service life). Sorry just thinking out loud.
I honestly feel the 110 was a good choice @ this time.

I know gear oil is probably a petty thing to concern myself with a new Ram but this will be my last tow vehicle & I honestly want it to take me well into retirement & beyond. So long term planning/thinking is in full motion at this point & time.
Close monitoring of all fluid temps & service life is top priority.

SyN Disclaimer: Note this question is only for the AAM 11.5” whom tow med/heavy loads for hours on end for 1/2 or most their working days. (NOT) daily drivers whom never get used for their intended purpose.
In which I know & take into consideration: Climate / Driving Style/Habits play a large role in gear oil viscosity as well or at least should.

 

[Ozymandias]

I thought RAM built this Truck to pull 30K all Day long?

 

[SyN]

Ozy: That is some real good Way Outside the Box thinking right there.

 

[6V92TA]

I thought RAM built this Truck to pull 30K all Day long?

I wouldn't confuse a pickup trucks max tow rating for any warranty of durability or suitability for that type of use.
I know if I was pulling 30k all the time I'd be in a class 7 or 8truck

 

[Ozymandias]

Ozy: That is some real good Way Outside the Box thinking right there.

Well I just think about Engine Oils, 15 Years ago I used only 15W40 in all of my Cars, today I have 5W20/30 in all Cars around. Never expected this.
Also 15 years ago i used the 75W140 Gear Oil in the (known weak) Rear Axle of my Grand Cherokee - as Jeep indicated for heavy Towing.

Why should we Not trust in RAM today? Today's Oils are sure far better than they have been in the Past.

And last but not least - the AAM Axle have very few Problems over the Time as we learned. I did not find many Threads here in the Forum complaining about premature failure.

 

[SyN]

I myself: When I hear first hand ——->We recommend this viscosity due to the MPG increase ! (To me that throws up a red flag!) Just like 5W-20 (Cafe) engine oil. Now there is 16Wt.
Like I said I have never read or heard: We recommend the 75W-90 due to higher quality shear ability & higher quality viscosity improvers for less wear & increased longevity over the heavier viscosity gear oils 110 & 140. (I just have Never seen or read this.)

This is just how I think & wired.
I apologize I’m just not apart of the flock & a follower.

Every owner has their own way of thinking & views.
Nothing wrong with that.
Thanks Gents for your replies: All are highly noted.

 

[6V92TA]

Syn, you aren't going to hurt anything staying old school except losing that that fraction of a percent in fuel economy. do what you want.

 

[SyN]

Oh I knew or know I would never have a issue.
To many positive results posted/reported after switching to a heavier viscosity.
It’s only machined metal gears & bearings.

It’s all about Shear stability & Film strength in my eyes.
I never had intentions on buying my new RAM to concern and worry about MPG.
My only concern is the adding the highest quality fluids & lubricants for the longevity of my ownership (which will be over the next 10-15 years.)

I need to find owners who have installed aftermarket rearend covers w/temp sending units & have monitored these temps closely while towing.
I still am very interested in hearing from owners whom have refilled with a heavier viscosity (75W-110 or 75W-140) & hear their final thoughts about the switch: ——->Positive or Negative results.

Thanks again gents!
Good Times Ahead

 

[STEVEBROOKS]

Oh I knew or know I would never have a issue.
To many positive results posted/reported after switching to a heavier viscosity.
It’s only machined metal gears & bearings.

It’s all about Shear stability & Film strength in my eyes.
I never had intentions on buying my new RAM to concern and worry about MPG.
My only concern is the adding the highest quality fluids & lubricants for the longevity of my ownership (which will be over the next 10-15 years.)

I need to find owners who have installed aftermarket rearend covers w/temp sending units & have monitored these temps closely while towing.
I still am very interested in hearing from owners whom have refilled with a heavier viscosity (75W-110 or 75W-140) & hear their final thoughts about the switch: ——->Positive or Negative results.

Thanks again gents!
Good Times Ahead

I've run 75W-140 (and 75% of that has been Mobil 1) for the 180,000 on my truck, and it's used mostly to haul my (admittedly) over-weight toyhauler 5er (and a tag-along flat trailer behind that!) during NM summers. The truck has never been abused, and it never will be, but buddy let me tell 'ya that truck has been worked HARD. I myself don't give a !@#$ damn about fuel mileage, the truck is a tool to get me and my family to where we want to ride, and I want the longevity and peace of mind that (to me) using only the best equipment/add-ons/lubes/etc can provide. Unsolicited recommendation: use Mobil 1 75W-140 and be done with it...

Steve

 

[SyN]

Thanks Steve for sharing your experiences! Big Fat Thumbs UP!

 

[Killgore]

Syn, I'm running 75W-140, pulling our fifth-wheel home which weighs about 20,000 lbs. I installed the PML cover from Geno's and an Isspro gauge that I closely monitor. Temps typically climb to 210* when the ambient is in the mid-nineties. On the other end of the driveshaft my G-56 (the older AD version) has Delvac 50 in it in lieu of Mobil Trans SHC now that it's unavailable, Fast-Coolers from Geno's, and another Isspro temperature gauge. I've found that monitoring these two gauges usually means that I'm forced to slow down to 63-64 MPH when the transmission temps approach 220*. The transmission is over-filled by one quart as recommended. I guess it all comes down to how great is the fuzzy factor? I have a warm and fuzzy feeling but I watch everything closely.

- Ed

 

[SyN]

Mr Ed: Many thanks for posting your personal experiences!

Thank you!

This is a pic of my transmission temp towing our 13K lb enclosed trailer. Ambient temp was 94°F.
This was a 137 mile trip average speed was 60/65mph.

I will stay with my RL-75W-110!
I will service the Rearend unit every 30K miles.
(I will barely accumulate 6K a yr since I have a company wk truck).
I don’t tow 24/7. 15Klb will be my max.

 

[SyN]

Going to use this @ the 10K mile mark to suck out the FF gear oil in the rearend & refill with the RL 75W-110.

Also use this with my 68RFE @ refill with Schaeffers All-Trans.

 

[JR]

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.