Is it necessary to change the diff. oil?

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I've seen several owner's manuals and they all stat that it isn't necessary to change the rear differential oil. Why do people still do it and how often is there a rear diff casualty?
 
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I have yet to own a vehicle equipped with a rear differential that specified not to change the fluid, what vehicles are these?
 
Don't forget that the differential is not exposed to the debilitizing acids that are formed in the presence of moisture or petrol. The only thing that will break down rear diff fluid is the shearing action of the ring and pinion.

I would still change it every 50k or so.
 
I had a 97 Audi A4, for which the manual stated the rear diff and entire drve line were life time fills not needed changed. Needless to say I changed them at about 40K intervals.
 
i change mine every 75k with a tune-up, needless to say I always check the fluid level every oil change.
 
Much depends on how hot the differential runs. Modern differentials are being made smaller, lighter, (more cheaply made), and stress the oil harder...thus the requirement in some for synthetic gear oil. The hotter the oil runs, the quicker it'll oxidize. Oxidized oil must be dumped and replenished.
 
My diff fluid was black as night after 8k> Itwas swapped with Amsoil and 13k later still looks great. The transafer case fluid looked horrible at 20k. Glad I changed mine.
 
Disposable vehicles don't need maintenance.

If you plan on keeping the vehicles in the family a long time, and don't want to have any unexpected failures, maintain the vehicles.

Marketing departments create your owners manual. The manual is not written to make the vehicle last forever. The owners manual is written to lower the cost of vehicle ownership so that you can buy a new vehicle in a few years.
 
Most of the break-in wear occurs in a differential in the first 500-1000 miles. So, I usually swap out the factory fill at 3-5000 miles for synthetic. After getting stuck with a bad front diff on my GMC and no help from GM, I will drain my diffs & tcase on my 4Runner at 30,000 miles and if the oil is black have a used oil analysis done while still in warranty. If there is accelerated wear, I'll be in the dealer pronto.
 
Originally Posted By: Popinski
Hyundai Genesis

Jeep Cherokee

Dodge Dakota

The manual just says "inspect".

Check the severe service schedule. I bet it says to change Diff oil every 15K miles.
Toyota Tacoma's oil was nasty at 15K miles.
Do not forget differential breathers. If they are stuck open/closed, differentials will suck in water thru the breathers/seals.

If you have a 4WD, remember your transfer case too.

When was the last time you checked those?

Dealer-speak "lifetime" = "while-under-warranty"
 
For most of my Explorer's life (pre-BITOG days) I never changed the diff fluid. I drained out the factory fill about a year ago (14 years and 140k miles). It was very nasty and a little foamy. It looked like there was some water in it. It's still fine and doesn't make any noises but I'm definitely glad I changed it.

That being said, most people probably never change their diff fluid and their diffs reach 200k+ miles with no problems. It may not be THAT necessary, but definitely a good thing to do.
 
If the diff gets under water, you will want to change it.

Many people tow boats, never think about this.

For what the oil costs, and what the service costs (if you don't do it yourself), then why not?

A shop charged me 15 dollars to change the rear diff oil on my 98 f150.

They took the cover off, cleaned out all the gunk, laid a bead of sealant, and refilled with the royal purple oil that I had supplied.
 
Originally Posted By: PW01
I'm sure it's extreme, but I change both diffs and the transfer case every 30,000 miles


+1
 
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