DODGE4X4

I am going to change out my rear diff fluid tomorrow. I have never run a synthetic before so I need help with a concern of mine. I have always bought the Mopar additive for my diff and I am wondering if it is needed with the Royal Purple. My truck has the posi rear end so do I need to get the Mopar additive or dose the Royal Purple take care of it? What weight oil do I need down here in the HOT South Texas,and what is the capacity ? Thanks

amartinson

I would use the 85-140 down there, especially if you do any towing. Supposedly, you don't need the additive, but if you hear some chatter a couple days after the change, I would add a bottle of additive.

amartinson

About 8 pints in the Dana 70, about 10 pints in the Dana 80. Fill to just BELOW the fill hole, or you could have axle seal problems down the road.

www.dodgeram.org has great specifications info if you need them in the future.

cville6

I have been using 85-140 Royal Purple and no additives in my posi rear end for about 20K miles now with no problem. I also have the 75-90 Royal Purple in the 5 speed. Seems to be working ok.

infidel

There is no set amount of anti-slip additive to use, it all depends on the clutch pack wear on each individual rear end. Start out with none and work your way up till the noise in turns stops. Too much additive and you no longer have a posi rear end.

HOHN

Or, you could have a setup like mine that gives almost no posi action at all EVEN WITH NO ADDITIVE

Frustrating...

jlh