There are no gaskets (at least not on mine from new and I do not use them) and no drain plugs on either of the diffs. Remove the covers to drain, clean the magnets, clean the covers, spray out and clean gears and cover surfaces with brake cleaner, apply a bead of black RTV sealant to the cover encircling all holes, install covers but only finger tighten the bolts. Wait 1 to 2 hours. Tighten the bolts. Wait over night. Fill the diffs.

Use ATF, do not use gear oil. Here is the reason. While these Cases (NP243D) do not have clutches like the 246, and are just gears and chain where gear oil would work very well ... the issue is the Tcase bolts onto the back an automatic transmission. There are oil seals between them, but everyone knows seals leak, even just a teeny smidgen. Anyone who has pulled a Tcase also knows that some oil is always found in the extension mating piece between the Tcase and the transmission. That means any oil in there is passing through the seals between the Tcase and the transmission. So, if you put gear oil in the Tcase and that gear oil gets into the extension cavity, then over time you will have some gear oil showing up in your transmission oil. Gear oil in an automatic is BAAAD! Unless you want to shorten the useful life of the transmission, always run the same fluid in the Tcase as what is in the transmission.
Therefore! .... if you have an automatic transmission, put ATF+4 in the Tcase. Only if you have a manual transmission would you consider to put gear oil in the Tcase.

AutomaticTransmission. ATF+4, 6 litres for dropping pan, 16 litres for a total run-through purge.
There are TWO filters in the 454RFE transmission. Get at both by dropping the pan. One is a flat type pan pickup filter. The other is a screw on, like engine oil filter. You can return the pan with a rubber gasket or just RTV using same method as the diffs. Neither is better than the other as long as it doesn't leak.

Coolant: 18 liters.
If you are doing a drain and refill (not flushing) then use Mopar HOAT compatible coolant ... unless you have put something else in at a previous service, then use that.
If you are doing a drain and flush then refill, you can put almost any coolant. Mine has been running just fine with Prestone in it since 2010. I flush and change out at 4 years.
Coolant is a mix of glycols and additives. The glycol and the additives are organics that have a shelf-life where over time they naturally break down, and they break down into acids. There are acid buffers, which they call corrosion inhibitors on the jug, which neutralize the acids. "Long life" coolant just has more buffers in it. Over time those buffers get depleted and then the acids level creeps up to where the fluid begins to attack cooling system components and leads to leaks. That shelf-life is 5 years on glycols. So not matter what the jug or the marketing says, change your coolant out at the 3 to 4 year mark unless you like mysterious coolant leaks on the driveway, milky oil in the drain pan, squeaky water pumps, or dripping radiators. My point being it is not so much as the coolant type, aka proprietary names, as the importance of the time period you allow it to get more and more acidic before changing it out. Change at 4 years or less. Anyone who has read this now understands the fallacy of any jug that says ###,000 miles life on it, I hope.


The stage that I am at right now is deciding on which lubricants to put in this time. Last change out of the trans and tcase of ATF+4 was using Mobil Super ATF+4. For the diffs, I use any decent quality big name brand synthetic gear oil that is on sale at the time.

I too at one time was sucked in by marketing and tried that purple stuff in this and other applications. Imho, the stuff is just crap. Makes a mess to clean up, you cannot tell from color what condition the oil is in, doesn't run any better or extend life any more than other good oils, and it is unnecessarily costly. There hasn't been any purple stuff in or around any of my machines for years. Don't waste your money on it. If you like purple, go buy purple flowers for your girl. I guarantee you will get a much better ride quality improvement out of the flowers, than by putting purple money in your truck.

Hope that helps!