I use the 75/140 AMSOIL in my rear diff with PML cover. I am coming up on my 15,000 mile interval and was ready to place a fluid order. I pull a pretty heavy gooseneck trailer on weekends only, live in a hot climate. Friend of mine has the same basic truck , same rear end, same size trailer and has been running the 75/90 for a LOT of miles with no problems. GOt me to thinking, Is the 140 really protecting better??? I have 5 quarts of 75/90 ready to go, would be nice to use it up and not have to order 140 or 110 until next OCI. Thanks!

 

75w 90 syn is recomended for all American Axles. Must be synthetic fluid because these diff's gets extremely hot.

 

I run 75W140 at my dealership's suggestion.

I think most likely the rear end would live a long life with 75-90, but that 75-140 would give a little extra margin of protection.

The price is the same (at least for Redline) so I guess 75-140 might not be absolutely necessary, but I don't see a downside if you tow in a hot climate.

 

I opted for the Amsoil 75-110

 

75w90 is-what is called for.The OTHER Chrysler axels (Corporate)in the other trucks call for the 140wt.I think the dealers push it so it fits which ever their servicing.I tow 90% of the time and use the 75w90. I asked AAM once a couple year ago and they were NOT using the 75w140.Lots of Chrysler dealers are using BG oil products and got on the 75w140 ban wagon.Even the 07 repair/maintance books call for 75w90 for the AAM axels.I think changing AMSOIL diff lube every 15k is big overkill.I'd at least roll it 30k if not more then that.

 

I agree with above, 15000 miles fluid change is way too short if you use Amsoil, this would mean change it every month for me and cost is not little.

The Amsoil dealer is a good friend of mine and he suggested replacing it at 50,000/60,000 if needed, but can go longer.

PS I tow 95% of the times too.

 

WWW.AMSOIL.COM has a chart on their recommended fliud run times.

 

There is a bulletin from Dodge that states fluid levels and types of fluid for diffs,

http://dodgeram.info/tsb/2004/03-001-04A.htm

Having said that my last change was dealer recommended 75W140...and it was not cheap from the dealer. I am considering using Redline or Amsoil 75W90 on this change.

 

Okay, so let me ask the dumb question, I'm runnen Royal Purple 75-90 in my Diff's, I don't tow, so could I go 30k before my next Diff change?

 

At least not towing.Not towing what does the manual call for? Not ever a change?

 

No it still calls for 15k intervall change, according to the book.

 

Both A and B service intervals call for 15k?

 

Run 30k on that fluid at least. Anything less is a waste. I use Amsoil 75/90 severe gear lube. Go ahead and pop that diff. cover off and you will see. Fluid still looks like new I beat, even at 30k. My next change is at 60k and I have a ways to go, only 48k on the clock. I do however find myself only driving it when I need too, otherwise it sits at the house, Last tank of fuel lasted a month...

 

WOW, what great responses. THe ONLY and I mean ONLY reason I am changing at 15,000 is because I want to maintain my warranty. Once that is up ( Almost there) Then I will go to the 30-50,000 interval. Thanks for the opinions! THe Book calls for 75/90 but I am wondering if the " Book" always has the best interests of the owners in mind?

 

If the 140wt was better AAM & Chrysler would call for it.They don't.Sometimes THICKER is not better.Fluid run off,clearances,heat dissipation with fluid run off. Until I see it in PRINT I will use the 75w90 under all conditions.