Was looking in my owners maual last week and noticed that they say to change the oil in both diffs every 15,000 miles. Whats up with that, I've never changed at that interval in anything I've owned.

 

I know what you mean. . .the change interval for my toyota is around 35-40K. but the dodge holding a bit over a full gallon in the rear is only 15K. doesnt make much sense, but you sure can tall a difference.

 

What fluid is everyone using for this. I was thinking of the royal purple 75-90. I do not tow anything. would that be a good choice?

 

When i did mine I think I used regular ole Valvoline oil.

 

yea, that will be fine. . .I'm running amsoil 75-90 right now and it is a VAST improvement over stock. there is also a 75-110 out there as well that is supposed to be even better.

 

my brother in law has a 99 3500 ctd and uses it hard on his farm - towing equipment, livestock, and hauling stuff. he never does any maintenance until something actually breaks down. he had a piece of land rented a few years ago where he had to ford a creek to get to it. sometimes the creek was down, sometimes it was up, he didn't care just drove through it. the rear end went past roaring all the way to shaking. when they pulled the cover it had more water in it than oil and the whole thing was shot.

the recommendation of change every 15k is
1. if people do it, the dealer service shop can make a lot of money.
2. they know that most people won't do and it can be a reason to deny warranty.

 

I am pretty sure on the 06 there is nothing saying every 15k. I looked just the other day. I am planning on doing it anyway at 20k and adding a mag-hitech cover. I know I have the 3.73 gear but how do I figure out if I have a dana or A.A ?? Its a 2wd by the way.

 

Drew, what do you mean you can tell a difference? Is there a performance difference after you change the oil in the differentials?

 

cracker, if your truck was made after 03, you have AAM axels.

 

Count the number of bolts on your rear diff cover. You probably have the AA rear axle with the 11.5" ring gear. It has 14 bolts. If you have a Dana 70 or 80 it will have 10 bolts.