I'm changing oils and going to synthetics in the differentials what are the recomended weights for each. And in the locking rear will I need an additive?
I haul a camper I seem to remember I need a different weight for heavyer use.

 

Out here in hell I run 75-140 synthetic. If you have the "posi" you will want to add the friction modifier from Mopar.

 

Thanks - Valvolene 85w-140 for the rear is what I'm planning on.

 

Dodge calls for 90 wt in rear and 80w-90 in the front. These are for the 2500 & 3500.
Due to a lot of heavy hauling I use a high grade, synthetic, 80w-140 in both and have had excellent results. Runs quieter and I get no shiny metal shavings in the pumpkins, so I assume it penetrates everywhere!
For heavy loads, that would be my recommendation!

RJ

 

Mopar wants the synthetic 75w-140 in the rears if you are towing. I put in in both front and rear of my 2002.

 

Check the oil you are buying. I bought Royal Purple synthetic and it claimed to already have the aditives in it for LS diffs. I suppose it is correct because it is actually working now. Got me out of a real jam and the boat launch a few weekends ago (I'm 2wd). I bought a tube of friction modifier but never added it.