My owner's manual states that the 5.7L engines use 75W90 and the 3.5L engines use 75W140. With the LSD you will also need a small bottle of LSD friction modifier. No difference listed between 6 speed or automatics, for rear axle lube. Call the dealer parts department, give them your VIN number, and they can tell you what your car left the factory with. If you're interested: MOPAR- SAE 75W90 synthetic rear axle lubricant (#68218655AA), need 2 quarts @ $14.75 per qt., and one 4 oz. bottle of limited slip differential additive (friction modifier), (#04318060AB) @ $5.90. Hope this helps.