I just bought a 2003 Dodge 2500 4x4 Diesel with about 130k miles on it. Its a 6 speed standard. I thought it'd be a great idea to change out the diffs and trans oil. What kind of oil do you run in the transmission? And if anyone is firmilliar, how much oil does it take? I thought about 6 litres? Also what is the proper oil for the front and rear diffs? Do you need the limited slip additive in the rear? Thanks guys.

 

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It sounds like you have the NV5600 transmission, which requires a synchromesh oil. Personally, I would use the Amsoil version (link), but any synchromesh oil should be fine. It should take slightly less than 5 quarts to fill your trans.

For your differentials, use either 75W-90 or 75W-110 gear oil. I use the Amsoil Severe Gear. If you tow very heavy loads the 75W-110 is probably best, otherwise stick with the lighter one.

You probably have the AAM 11.5" rear diff, which has a massive case with a 14-bolt cover and holds almost four quarts of oil. The front should be an AAM 9.25" which will hold about 2.5 quarts. For both diffs, you should fill them until the level is about 1/4" below the fill hole. Generally, the 11.5" AAM rear diffs use a geared limited slip setup that has no clutches, so you do not need any special additives. The front diff should not have a limited slip unless someone added an aftermarket one.