2003 Dodge Ram 1500 4.7L 9.25 rear 2WD.

I think I read it somewhere but I can't find it or I'm not looking right. I'm having new gears installed next week and do plan on using 75W-140 RP oil, but for the 500 mile break in, would rather not spend a lot of money ($19/qt.). Would it be okay to use the lower cost ($4/qt) 85W-140 gear oil with friction mod additive for the first 500 miles and then change it to the RP? Shouldn't damage anything, right?

I'm in south Florida where it doesn't get very cold here so thinking the 85W should be okay or should I get 80W-90? I don't think I could find anything else on the low cost below 80W.

I'm probably not going to like the answer but hey, that's what this site's here for!

 

Oh, I'm just doing a straight ring/pinion swap. Not upgrading the LSD.

 

Inexpensive, conventional oil is fine for the break in period. It only has to last 500 miles and it's gonna get fine particles in it anyway. Might even get some broken "C-Clips" in it too! I'd seriously consider having the LSD replaced when they are in there if the unit is the stock one still...

 

and one more question ... sorry .... if I use Royal Purple synth 75W-140, do I need to add the Friction modifier?

 

It is included, however I found I had a little chatter with RP in my Grand Cherokee (Vari-Lok kinda a hybrid between an LSD and lockers that requires the modifier) and found I had to add a little extra so they were dead quiet. My advice, just go with the RP by itself first. The LSD will "tell you" if it needs some stand alone friction modifier, trust me...

 

Judging by your vast knowledge, how can I not? Thanks for the info, Hammer!