Rear differential fluid change?

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jkayca

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Page 500 of my 2014 manual says the same thing. However, on page 340 it says "Your vehicle's rear axle is filled with a synthetic rear axle lubricant and is considered lubricated for life. These lubricants are not to be checked or changed unless a leak is suspected, service is required, or the axle has been submerged in water."

I think I found where I messed up...unless service is required...I missed that. So, service is required on the rear diff at 150,000 miles, which I guess is Ford's definition of "life.". So, when it gets to 150,000 I'll change it. Thanks for motivating me to go back into the manual and take a look.

FWIW, I just had the front diff passenger side axle seal replaced today...pesky seep. We checked the diff fluid and it is a really dark/black and well-used color...not healthy looking at all. Will be changing that out right away. Odd, though...because I have hardly ever driven the truck in 4WD...not even 5-6 miles on snow and once up a steepish muddy track...although it had about 28,000 on it when I bought it...maybe previous owner?? Truck was immaculate when I purchased it.
Rear diff is always in use. I think you maybe thinking of the transfer case. I don't know if the two are in the same unit on the Expedition and therefore share gear oil. Either way, the fluid in the rear diff is going to get used even in 2 wheel mode as the Expedition is rear wheel drive when in 2 wheel mode.
 

WEDGE

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Rear diff is always in use. I think you maybe thinking of the transfer case. I don't know if the two are in the same unit on the Expedition and therefore share gear oil. Either way, the fluid in the rear diff is going to get used even in 2 wheel mode as the Expedition is rear wheel drive when in 2 wheel mode.
Rear diff and transfer case DO NOT share oil. Only thing they share is the rear driveshaft
 

Trainmaster

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As others have said, millions of cars out there and probably 99% have never had the rear end oil changed. Virtually none of them fail. Spend your money elsewhere, unless you just want to be very safe.
 

07navi

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I ag
As others have said, millions of cars out there and probably 99% have never had the rear end oil changed. Virtually none of them fail. Spend your money elsewhere, unless you just want to be very safe.
I agree, it sounds like it's horrible to leave it in but it's synthetic and no contaminants like elsewhere. The only thing that kills them is water and leaks.
 

WEDGE

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I recently changed the rear diff and transfer case oils in my 2010 and my sister's 2007 Expeditions. I don't believe that "lubed for life" B.S. Oils break down, they do not last forever. Ever seen the transfer case or "PTU" in a Ford Edge NOT blow up? They're sealed units from the factory and only hold a quart or so of oil. They burn up the oil all the time. So yes I would recommend changing the diff oils.
 

Vancouver Bob

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It's settled... based on opinions, you should either change it or just leave it :). You're choice.

I didn't change mine until I had the gears changed. That was at over 200K miles. Then changed it again some miles later as recommended because of the new gears (and lockers). If not for that I wouldn't have touched it. But that's just me.
 

ExplorerTom

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Then changed it again some miles later as recommended because of the new gears (and lockers). If not for that I wouldn't have touched it. But that's just me.

So what’s the difference between factory installed gears on the assembly line vs new gears at 200k miles? Why change the oil after 500 miles on the gears installed at 200k miles but yet the factory installed gears are somehow “lubed for life”? Does the factory use special gears/bearings with special lube? Spoiler alert: they don’t.
 

07navi

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It seems like you should change it but it
So what’s the difference between factory installed gears on the assembly line vs new gears at 200k miles? Why change the oil after 500 miles on the gears installed at 200k miles but yet the factory installed gears are somehow “lubed for life”? Does the factory use special gears/bearings with special lube? Spoiler alert: they don’t.
He changed it because somebody said it was recommended on the new ones (for no good reason) and it was apart so he changed it. Yes the factory does use special synthetic oil but gears are gears............very hard. I might add that I specialized in transmissions and rear ends when I was a mechanic.
 

Vancouver Bob

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So what’s the difference between factory installed gears on the assembly line vs new gears at 200k miles? Why change the oil after 500 miles on the gears installed at 200k miles but yet the factory installed gears are somehow “lubed for life”? Does the factory use special gears/bearings with special lube? Spoiler alert: they don’t.

You mean the difference between factory gears installed at the factory vs third party gears installed by a fourth party? I can think of a short list of things. That said, Nitro gear has specific break in instructions for their gears. For seemingly good reasons and that's why I changed the oil. For comparison, there were no gear break-in instructions when I bought the Expedition :).
 
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