When to replace differential/transfer case oils

My maintenance schedule states to only replace the front and rear differential oil if you drive primarily in dusty conditions, heavy loads, and towing. The same is for the transfer case oil too. I do not drive my truck in these conditions. None of the maintenance scheduled miles intervals does it state to replace them at all. Should there be an interval that you should replace these oils though?

 

Shop I use recommended 150,000 miles.

 

When I found out my tranny was 3/4 low from the factory, I checked and replaced all fluids. Now I know.

 

I do mine every 30k miles, it wasn’t difficult or expensive

 

30k, front and rear diff Redline 75w90, manual transmission and transfer Redline MT90, and life is good.

 

Consider changing them at the 60k or 90k mark, it’s probably not necessary but cheap insurance.

I change at 30k due to occasionally towing a boat, probably not necessary, but anyway…the transfer case oil always looks fairly new. So it seems to be the one that is least in need of replacement.

 

30k is the recommended. More importantly for the rear diff. If you're not really using the 4wd, I suppose you could make the front interval longer (45k?) either way.. after 30k for me is like 5 or so years, so why not change the fluids after so long?

 

You sure about that? You need to read the first post and the maintenance guide much more closely.

 

Interesting how it says to only inspect the rear differential oil after 30,000 or 36 months. Reminds me of the "Lifetime transmission fluid" from some Toyota/Lexus vehicles

 

That’s basically what it is, a lifetime fluid if normal use, with a replacement interval for what I guess one might call more severe use.

No harm in going ahead and doing a $30 DYI oil change every 60 or 90K. I’m not sure what one is looking for if inspecting the oil, kinda doubt anyone does that unless it’s the dealer doing scheduled maintenance under a care plan or dealer extended warranty requirement.

 

In my opinion, the first change is the most important. I changed diffs and manual transmission/transfer case at 30k and every 30 or so since.
The first change looked like it needed it (except transfer case, it was pretty clean), after the first change, the gears are pretty worn in and subsequent changes showed pretty good fluid coming out.
It's easy enough to do that I do it pretty much every 30k. I am not talking about automatic transmission transmission fluid here since mine is a manual.
I usually stick a finger in the front diff at around 30 and it looks clean so I go a little longer on it. I don't use 4WD very often.

 

The rear diff fluid is definitely not a lifetime type of fluid, but I get what you're saying. Replace as needed. The important thing is to make sure you're checking to see if it needs to be changed. I'm like others and will change every 30k or there abouts. I will say my first change was at 60k and the rear fluid was a bit dark, but not concerning since it didn't have metal flakes. My truck is driven only on-road. I don't tow normally. Maybe a handful of times in the 10 years I've owned it. I recently changed it again and the rear diff could probably have gone another 30k without needing a change. The front looked brand new because it rarely gets used. Oddly enough, the transfer case fluid was darker than the rear diff fluid.

 

The better wording would be, under normal use the rear diff fluid does not have a replacement interval. It’s replaced on condition only, meaning only if inspection of the fluid shows an issue.

I just wouldn’t know what that inspection would show that would drive me to a replacement. What’s the criteria for change? Metal particulate? Evidence of water intrusion, milky color? How dark the fluid was? Tastes like chocolate milk?

 

Don't know about tasting like chocolate, but yes to the others. That's just my opinion. Drive it until it breaks if you want. It's your truck.

 

I change the fluid every 30k because I meet the Special Operating Conditions.