Originally Posted By: Zaedock
I think you already lost the warranty on the rear when you installed the Auburn.
Yup, the poster above is 100% correct.
renos09ram;
You have altered/moddified the rear end by changing out the LS unit so your warranty on it( 3/36 and any extended power train warranty )is pretty much now voided. If a non related part to the LS unit fails such as a bearing they are not going to cover that most likely because you got in there and altered it. They "might" but I doubt it unless the dealer installed it. Even if they decided to if they see you went with an 80W-90 conventional instead of the spec'd 75W-140 they absolutely will not cover any of the other parts. Guarantee if you change the LS unit out and run a fluid other than the OE spec one your warranty is long gone.
Just keep in mind the Dodge 1500 rear ends run very hot which is why the OE fluid is a 75W-140 synthetic. You better plan on changing the fluid every 10K or so. I would add a larger aftermarket diff cover to increase fluid capacity and help with cooling.
Also, you said...
Originally Posted By: renos09ram
I can buy Royal purple in a 75w 140 non synthetic.
Where did you see that or who told you Royal Purple offered a non synthetic 75W-140 gear oil? RP MaxGear is a full synthetic synthetic gear oil.
Originally Posted By: RoyalPurple.com
Max-Gear is an ultra-tough automotive gear oil. It’s designed to maximize power and provide unsurpassed protection to heavily loaded gears. It makes gears run smoother, quieter, cooler and longer without overhauls.
Max-Gear outperforms other gear oils because it combines the highest quality synthetic oils with Royal Purple’s proprietary Synslide additive technology.
Max-Gear is recommended for use in truck, motor home / RV, and automotive front or rear differentials, manual transmissions, and lower gear units of marine engines that specify use of an API GL-5 or GL-4 fluid. All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary.
http://www.royalpurple.com/gear-oil.html
I don't really know what to tell you. As I said the Ram 1500 rear ends run very hot which is why Dodge spec'd a heavy synthetic gear oil to be used. I would definitely keep it changed often if running a 90 weight conventional oil.