OK, Im planning on changing my differential fluid before I head out to Wyoming from Wisconsin. I read that pulling a trailer that I should be running 75w-140 in both front and rear diff's. Is this true? Or should I just run the 75w-90 in both?

Also I bought the PML covers for the front and rear. Does anyone know how much more fluid they hold with this type of cover on?

 

75w90 or 75w140 both work just fine. Make sure it is a synthetic product i.e Royal Purple, Mobil 1. Synthetics have a higher temperature range. Hope this helps.

 

^^
He has a 2500, so that could change things as well. Realistically you could run either weight, but if you tow at all I would recommend the 75W-140.

Stock capacities are ~2.5 qts up front and ~3 qts in back. most increased capacity pans add ~1-2 qts.

nateroach

 

Thanks guys. I went with the 75w-140 Royal Purple. It's what the dealer said to run as well.

 

Ahh did not see he had a 2500. Good Choice on the RP. You wont be disappointed.

 

I run 75w-140 RP in the front, changed every 30k miles. 75w-140 Lucas conventional in the rear with their friction modifier, changed every 15k miles.

You don't need to bother with the conventional in the rear like I have to. The RP is a good choice for both. Normal use with occasional towing then 30k changes. Tow often or real heavy and change it every 15k...

 

What Dodge recommends as far as weights, they're already full synthetic. Royal Purple already has the friction modifier in it, btw.

 

I have a 2008 1500 4x4, is ok if I run 75W90 in front and rear? Ill prob go with royal purple seems to be the best choice...

 

yes that should be fine. otherwise call your local dodge service center and ask them. go synthetic.