Harwill,
My 03 manual is the same. My last change went to 75/140 and the rear end howl went away. I decided to go up from advice from here.

Cya

 

Make sure you clean the outside of the diff case around the gasket area and on top before you take any bolts out. Use a stiff brush to get at the space above the gasket and between the case and cover. You might even try some brake cleaner or what have you.

I you don’t dirt and debris will fall on the ring gear since it sticks out past the case. Throw a clean rag or towel on top the ring gear when you get the cover out too, then check to make sure the gears are clean before you put the cover back on. Wipe out the bottom of the diff case too.

These AAM axles are quite stout, but even they won’t put up with contamination. I threw a strong magnet in the bottom of mine to help out the magnetic plug.

 

Wally World 75-90 synthetic works nicely!

 

The change to 75/140 gear oil was only for the smaller rear ends in the 1/2 ton/1500 trucks and not for the 10.5 or 11.5 rear ends. I talked to Dodge when this first came up last year and was shown that it only applied the 1/2 trucks not the 3/4 and 1 ton trucks.

 

Hounddog,
Most of the failures I've heard of were the 1500s and I think the previous posts sorta bear that out. Did find another reference to axle fluid change in the '07 owners manual (pg 411), "Vehicles operated in normal service do not have regularly scheduled oil changes". So the official word is 15k miles or Never?
Sounds like lawyer talk...

 

I thought that Chevy and Dodge both used AAM axles?

My 2003 Dmax had a removeable plug on the bottom of the axle. I have not looked close enough at my current Dodge to know if it does or not?

 

from what I've gathered you're supposed to clean to outside of the diff with brake kleener. Anything any particluar used to clean the gasket, or the gears/inside of the diff once the cover is off?

 

Brake cleaner. GM and Chrydler both use AAM axels but they are slighly differant from each other.Drain plug being one differance.

 

I cleaned the inside with brake cleaner. Wiped down the inside of the case, and just wiped off the gasket with a dry rag. Just make sure everything is clean and dry and you will have no issues. DO NOT OVERTIGHTEN THE COVER BOLTS!!! They do not need much torque, there are many people that have snapped them off.

 

Just did both diff's with Mobil 1 75-90 synthetic. Seems to have improved the feel of the truck drive line, then again the stuff I drained out had the viscosity of water. Have 20k on truck, and I am going to start pulling a camper starting tomorrow.

 

alright, brake kleener on the gears, let it dry, and wipe down the gasket...sounds simple enough. Thanks everyone.

 

Actually I don't use brake cleaner on gears.I wipe out the bottom of the pumpkin and leave it at that.I don't WASH wheel bearings eaither.I wipe them clean and inspect then lube.Some think tyou do more harm washing the gears then just leave them and side bearings oily and inspecting.I'm one whom feels that way.

 

Went with the Lucas 75w90. Had good luck with their products before. We will see how she runs. It was all about the same price, with the mobil 1 being a dollar more a qt, and the royal purple was the same as the lucas.

 

I am also wanting to change my diffs soon. Would 80w-90 be ok to use without causing any problems?

Also would 7 quarts be enough for both front and rear?

Thanks

 

I would think 80-90 would be OK just make sure its GL-5 synthetic gear oil as that is what it came with 75/90 synthetic from the factory and what it requires per AAM. It took 7.5 Qt's to change both of my diff's.