For my 2004.5 Dodge 3500 CTD this is what I think I need to do based on researching the forum and some advice from members and discussions with the local dealer. From what I understand this is fairly easy.:

NV5600 Manual - Remove the fill plug on the side. 17mm Allen Remove the lowest bolt from the PTO cover. 14mm Socket Drain. Put bolt back on PTO cover. Use about 4.5 quarts of AMSOIL MTF to fill it back up to the fill hole.

Transfer Case - Remove the fill plug on the front of the transfer case. 10mm Allen. Remove drain plug. 10mm Allen Replace drain plug. Fill to fill hole. Going back with ATF 4+ got 2 quarts.

Rear Diff - Remove the cover. Clean the gasket since it is reusable. Wipe out. Put gasket back and replace cover. Fill to the line that is faintly marked on the cover; which should be slightly below the fill hole. Going back with 4 quarts of AMSOIL 75-140 Severe Service Gear.

Front Diff. - Remove the cover. Clean with gasket since it is reusable. Wipe out. Put gasket back and replace cover. Fill to the fill plug hole. Going back with 2.3 quarts of AMSOIL 75-90 Severe Service Gear.

If I am missing something important here or have any advice please let me know. Thanks for the help.

 

Check your manual for your rear diff, you should be running a 11.5 which requires the 75w-90 vice the 75w-140

 

I thought 75 90 was thin so I called my local dodge dealer. They said they often put 75 140 back in on the 3/4 and 1 tons. So I thought other than being a couple bucks more there would be no disadvantage or harm. Am I incorrect?

 

Ask the dealer to put it in writing.

If you're towing regularly and/or heavy, the 140 will offer better protection. Otherwise it might be a bit too thick. There is some debate on this, 90 vs 140 and if any problems can arise. So, you'll hear both ways.

 

Take the PTO cover right off - both sides and clean out the gunk that is bound to be in the bottom of your NV5600.

 

I am going back with 75w90 in the front since they did not have enough 75w90 Ams in stock and I did not want to run back to get more. So I guess the answer is it was just easier to use the Mobil 1 since AMS was out of stock.