markm4

....that is the question...wether tis noble-r to change it out if it looks a little "not so fresh" or to sucum to the slings and arrows of the parts counter guys who in their tyrany say "just top it off" "I never change that", "changing it will cause it to break"

oh Juliet, what shall I do. The humanity

Mark

TonyB

Not waxing too poetic, are we?

When in doubt, change it out! I change my '06 gear oil every 15k (per owners manual). My F150 was supposed to be 'lifetime'. I installed a mag-hytec cover at 30k, and the fluid WREAKED! Nasty old oil! After that I changed it 1/yr regardless of miles, though usually had 15-20k/yr.

HTH

Tony

infidel

I change mine every 75k.
I know looks can be deceiving but it has always looked fine.

92DuallyCTD

Ah, but it isn't all in the looks that matters...those of us in the know, know that it's all to do with the TASTE!! (may hold true for any number of things; lubricating oils, food, women..you name it!)

FirstDodge

Changed mine in my '06 at 10K, and will change it every 50K or so. I put synthetic in it . . . . not sure what comes from the factory.

markm4

The parts counter guys seem to be in the minority on this one. They said it would increase the pressure and blow my seals if I went to nice clean oil after a very long time of running with old oil in my rear differential.

Mark

92DuallyCTD

They said WHAT??!! First you must understand there is no actual pressure(to speak of) on the seals to begin with...and even if there was(which there ain't)...the OLD oil would exert more pressure due to being 'thick and dirty' than any new and clean oil would!! Keep in mind pressures don't enter into the equation of rear diff fluid seals in the first place. Don't know about you, but I think I'd be finding another parts counter to deal with, right? And I'd agree with the above posts of changing fluid at purchase time for sure. About the only other thing to be aware of is whether the diff is Trak-Lok(Power Lock, Sure-Grip, posi, whatever the flavor is this week...) and then you'd need to add a bottle of Jen-U-Wine Mommy Mopar friction additive to it. My usual $1.53 worth.

Fueling around

Change to synthetic of your choice.
The worst you can do is overfill the diff which does cause pinion seal leaks.

92DuallyCTD

John, just curious, but how is it over-filling would cause a pinion seal leak? I can see where it may cause an axle seal leak...is that what you meant? Also need to append my previous message with the note that a plugged axle vent COULD create a SMALL amount of pressure(I suppose), as the gears churn up the diff fluid. But again I would think that highly unlikely enough to cause a true pressure leak - probably far less than 1psi - at the pinion or axle seals. But then, in this less-than-perfect world...

jwb600

if you dont think it is fresh change it out. I think fluid is alot cheaper than buying a rearend or ring and pinion

Fueling around

Nope pinion. Seal won't hold in oil in a constant bath. Designed mostly to keep dirt out.