When, for my 07 Dodge 5.9, am I supposed to change the front and rear diffs. I have automatic transmission, when should that be changed too?

I think I want to change the diffs to Amsoil.

 

check the owners manual it gives recomendations. But if you want to change to amsoil just do and get it done. Never hurts to have good clean oil in the diffs. the trans I was told to change every 15k but everyone has their own ideas

 

Many change those diffs at 5000 or so to get that breakin material out. The tranny can wait, 20-30k is a good range, unless you want to get the synthetic in there.

 

For 2006 it was 15K for the diff's and 30K for the trans and trans filter. If you run Amsoil SVG gear oil in the diff's you can go a lot longer then 15K. If you also use Amsoil ATF then after 2, 30K changes you could extend it to 50K or more.

 

I want to change out my differentials to Amsoil... which weight oil should I get?

Mostly daily driver town/hiway, tow loads occasionally short 50-75 mile runs. Putt around ranch in 4hi mode occasionally.

 

I use 75-110 Amsoil in the diffs and Amsoil ATF in trans. I do trans at 30k. front diff about 30k and rear about 20k.

 

The 75W-90 will work great for both diffs. Some, like Marine, use the 110 in the rear for just a little added "cushion" for towing. Can't go wrong with either.