I have an 08 Ram w/Cummins that I bought new. I changed all the fluids last year. The book calls for changing the front & rear axle fluid every 15k miles. At 15k,30k,45k,60k and on. I changed the front & rear at 30k along with the transfer case & transmission. About half of the 30k miles were towing a 5er. Just weighed it before leaving Florida a month ago and the gross weight was 13,500. There was very little metal on the rear magnet or bottom of pumpkin. But change every 15k miles seems a lot, so maybe a bigger cover to hold more fluid is a good idea. It called for and I used 75w90 synthetic in both front & rear. I have the limited slip differential and the book also says "limited slip additive is not required". I also changed the transfer case & manual transmission. Both called for ATF-4. I did not know until I changed the fluid that the standard transmission now uses automatic transmission fluid. Book calls for changing both at 60k miles, but since I was doing the pumpkins just decided to do it all.
