Did mine yesterday. I used Mobil 1 75-90w. Cheep insurance like said before. Oil that came out was nasty, brown greenish color and smelled bad. It might have still been doing its job but better safe than sorry. Easy job just a bit time consuming.
First thing I notice this morning is I don't have that annoying howling noise from the rear end.

 

diffs, trans, t-case once every year, engine twice a year for me

 

[QUOTE=Buffalo]I changed mine at 15,000 and replaced it with the Mopar fluids. The original fluid looked pretty nasty. A greyish/green color. With that in mind, I believe the first change is probably more critical than the others. Gets the wear-in material out.

I changed my factory gear lube at 2303km/1431 miles because I wanted to eliminate the metal particels from machining during fabrication. I am sure glad I did. When I loosened the bottom differential cover plate bolts the first dozen or more drops that emerged from below the cover appeared to be straight water drops. When the factory gear oil was in the drain pan it had a cloudy milky greyish color. There seemed to be little lubrication consistancy to the slurry. After I sprayed the crown gear teeth off with varsol the surface looked well rubbed or worn by the pinion gear where they contact. I took samples of the drain from the front and rear diffs. Both differentials appeared to have excess water in the lube oil. My truck has never been off the ashpalt road yet and I hope the dealer did not put water in the diffs.

 

The 2005 Ram Truck Diesel Owner's Manual states on pg. 365 under the sub-heading "Rear Axle And 4x4 Front Driving Axle Fluid Level": Vehicles operated in a normal service do not have regularly scheduled oil changes. If fluid becomes contaminated with water or subject to severe service, follow the recommended change intervals in Maintanence Schedule "B" of this manual.

NOTE The presence of water in the gear lubricant will result in corrosion and possible failure of differential components. Operation of the vehicle in water as may be encountered in some off-highway types of service, will require draining and refilling the axle to avoid damage.

 

I changed the front and rear diff oil in my 2004.4 last weekend at 14.6 K miles. The rear dif was loaded with metal particals. Front was better but plenty of wear material as well. Niether Dif was full from the factory, both took close to 1.5 pints more than came out!
I do not think that the gears or bearings are damaged but I would not recommend missing this oil change. I have done some medimum duty towing but mostly solo hiway driving.
I used amsoil 75W-140 SG in the rear and 75W-90 long life in the front. I love this truck. Consistantly pulls 22.5 mpg at 60mph and 20 mpg at 70 mph.

Jim B

 

I may be a little nutty but I dump out the rear diff around 1,000 miles. Then I do it at 15,000 miles and every 15,000 thereafter. Reason I dump it at 1,000 miles is due too the fact that you have a lot of wear metal that gets suspended in the oil during break in. That first dump looks nasty but the 15,000 mile one is much cleaner looking.

 

Hit a parts store like NAPA and buy your synthetic gear oil in a 5 gallon bucket and you can get the price down to less than $7 a quart. Buy a pump to fit the bucket and you are in business. Sure is a lot easier to pump it in than it is to use those quart bottles for me. I got Valvoline as that is what is in the engine.